U.S. patent application number 10/364303 was filed with the patent office on 2004-02-12 for inhibition of psychostimulant-induced and nicotine-induced craving.
This patent application is currently assigned to The General Hospital Corporation, a Massachusetts corporation. Invention is credited to Breiter, Hans C., Kosofsky, Barry E., Mandeville, Joseph B., Marota, John J. A., Rosen, Bruce R..
Application Number | 20040029872 10/364303 |
Document ID | / |
Family ID | 22025613 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040029872 |
Kind Code |
A1 |
Breiter, Hans C. ; et
al. |
February 12, 2004 |
Inhibition of psychostimulant-induced and nicotine-induced
craving
Abstract
The invention provides methods for inhibiting
psychostimulant-induced or nicotine-induced craving of additional
psychostimulants (e.g., cocaine or amphetamine) or nicotine. In
these methods, D1-like antagonists or D1-like agonists are
administered to a patient dependent on psychostimulant drugs or
nicotine and therefore susceptible to, or suffering from, such a
craving. Also disclosed is an animal model system useful for
measuring the ability of test compounds to inhibit
psychostimulant-induced or nicotine-induced cravings in humans.
Inventors: |
Breiter, Hans C.; (Lincoln,
MA) ; Rosen, Bruce R.; (Lexington, MA) ;
Marota, John J. A.; (Boston, MA) ; Mandeville, Joseph
B.; (Somerville, MA) ; Kosofsky, Barry E.;
(Swampscott, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
225 FRANKLIN ST
BOSTON
MA
02110
US
|
Assignee: |
The General Hospital Corporation, a
Massachusetts corporation
|
Family ID: |
22025613 |
Appl. No.: |
10/364303 |
Filed: |
February 10, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10364303 |
Feb 10, 2003 |
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09159659 |
Sep 24, 1998 |
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6517812 |
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60059838 |
Sep 24, 1997 |
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Current U.S.
Class: |
514/225.2 ;
514/282; 514/317 |
Current CPC
Class: |
A61K 31/4725 20130101;
A61K 31/438 20130101; A61K 31/496 20130101; A61K 31/4743 20130101;
A61K 31/5415 20130101; A61K 31/55 20130101; A61K 31/48 20130101;
A61K 31/00 20130101; A61K 31/472 20130101; A61K 31/4745 20130101;
A61K 31/4741 20130101; A61K 31/473 20130101; A61K 31/4515
20130101 |
Class at
Publication: |
514/225.2 ;
514/317; 514/282 |
International
Class: |
A61K 031/5415; A61K
031/445; A61K 031/485 |
Goverment Interests
[0002] The research described herein was supported, at least in
part, with funds from the Federal Government awarded through the
National Institute of Drug Abuse (under grants DA00265-02,
DA00275-02, and DA09467-03), and through the Heart, Lung and Blood
Institute of the National Institutes of Health (under grant
#39810). The Government therefore may have certain rights in the
invention.
Claims
What is claimed is:
1. A method for inhibiting a psychostimulant-induced craving in a
human, the method comprising: identifying the human as being
psychostimulant-dependent and administering to the human a D1-like
antagonist or D1-like agonist in an amount effective to inhibit
craving of a psychostimulant.
2. The method of claim 1, wherein the psychostimulant is
cocaine.
3. The method of claim 1, wherein the psychostimulant is
amphetamine.
4. The method of claim 1, wherein the human is a compulsive
psychostimulant user.
5. The method of claim 1, wherein a D1-like antagonist is
administered to the human.
6. The method of claim 5, wherein the D1-like antagonist is
selected from the group consisting of SCH 39166; SCH 23388; SCH
23390; A-69024; bulbocapnine; butaclamol HCl, (+)-; fluphenzanine
HCl; flupenthixol 2 HCl, cis-(Z)-, fluspirilene; haloperidol;
SCH-12679; SKF-83566; thioridazine HCl; thiothixine HCl;
trifluoperazine 2HCl; and trifluorperidol HCl.
7. The method of claim 5, wherein the D1-like antagonist is
administered at a dosage of 0.0001 to 100 mg/kg of the body weight
of the human.
8. The method of claim 1, wherein a D1-like agonist is administered
to the human.
9. The method of claim 8, wherein the D1-like agonist is selected
from the group consisting of A-86929; SKF 81297; SKF 38393;
A-69024, N-allylnorapomorphine HBr, R(-)-; apomorphine HCl, R(-)-;
6-bromo-APB HBr, r(+)-; 6-Chloro-APB HBr, (.+-.)-(SKF-82958);
Pergolide methanesulfonate, and SKF 77434.
10. The method of claim 8, wherein the D1-like agonist is
administered at a dosage of 0.0001 to 100 mg/kg of the body weight
of the human.
11. The method of claim 1, wherein the D1-like antagonist or
D1-like agonist is administered intravenously.
12. The method of claim 1, wherein the D1-like antagonist or
D1-like agonist is administered within 0 to 168 hours of
consumption of a psychostimulant by the human.
13. A method for inhibiting nicotine-induced craving in a human,
the method comprising: identifying the human as being
nicotine-dependent and administering to the human a D1-like
antagonist or D1-like agonist in an amount effective to inhibit
craving of nicotine.
14. The method of claim 13, wherein the human is a compulsive
nicotine user.
15. The method of claim 13, wherein a D1-like antagonist is
administered to the human.
16. The method of claim 15, wherein the D1-like antagonist is
selected from the group consisting of SCH 39166; SCH 23388; SCH
23390; A-69024; bulbocapnine; butaclamol HCl, (+)-; fluphenzanine
HCl; flupenthixol 2 HCl, cis-(Z)-, fluspirilene; haloperidol;
SCH-12679; SKF-83566; thioridazine HCl; thiothixine HCl;
trifluoperazine 2HCl; and trifluorperidol HCl.
17. The method of claim 15, wherein the D1-like antagonist is
administered at a dosage of 0.0001 mg/kg to 100 mg/kg of the body
weight of the human.
18. The method of claim 13, wherein a D1-like agonist is
administered to the human.
19. The method of claim 18, wherein the D1-like agonist is selected
from the group consisting of A-86929; SKF 81297; SKF 38393;
A-69024, N-allylnorapomorphine HBr, R(-)-; apomorphine HCl, R(-)-;
6-bromo-APB HBr, r(+)-; 6-Chloro-APB HBr,(.+-.)-(SKF-82958);
Pergolide methanesulfonate, and SKF 77434.
20. The method of claim 18, wherein the D1-like agonist is
administered at a dosage of 0.0001 mg/kg to 100 mg/kg of the body
weight of the human.
21. The method of claim 13, wherein the D1-like antagonist or
D1-like agonist is administered intravenously.
22. The method of claim 13, wherein the D1-like antagonist or
D1-like agonist is administered within 0 to 168 hours of
consumption of nicotine by the human.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
from U.S. Ser. No. 60/059,838, filed Sep. 24, 1997.
BACKGROUND OF THE INVENTION
[0003] This invention relates to inhibition of
psychostimulant-induced or nicotine-induced craving in humans.
[0004] The use of psychostimulants, such as cocaine, and of
nicotine often leads to repeated use and a profound state of
addiction in humans, which is characterized by compulsive drug use
and an inability to control use despite significant adverse
consequences. Cocaine, for example, is one of the most reinforcing
drugs known (Johanson et al., 1989, Pharmacol. Rev. 41:3-52).
Progress toward understanding the neural substrates of addiction to
cocaine and other addictive drugs has mostly been limited to
research with animal models. The use of such animal models,
however, has been limited by the inability to correlate observed
patterns of brain activation with subjective information about
emotional and cognitive responses to drugs, such as euphoria or
craving typically experienced after use of addictive drugs.
SUMMARY OF THE INVENTION
[0005] It has now been shown that a distinct pattern of brain
activation is exhibited by humans during periods of craving induced
by a psychostimulant. As determined by functional magnetic
resonance imaging (fMRI), psychostimulant-induced craving (e.g.,
cocaine-induced craving) is strongly correlated with early, but
sustained, signal changes (positive or negative) in the nucleus
accumbens and in the amygdala. In contrast, as shown below, the
cocaine-induced experience of rush is associated with a pattern of
brain activation distinct from the pattern exhibited during
cocaine-induced craving. As discussed in further detail below, the
studies described herein demonstrate that (a) humans have the same
extended neural network of reward circuitry as animals, and (b)
this circuitry performs both reinforcement reward and incentive
reward function (e.g., craving). These observations, along with (1)
observations from animal studies, showing that drugs specific for
D1 receptors alter reward processes in the brain and (2)
observations regarding the distribution of dopamine receptor
subtypes in the brain, indicate that agonists and antagonists of
the D1-like receptors can be used to inhibit craving of
psychostimulants in humans, with or without inhibition of euphoria.
In addition, such agonists and antagonists can be used to inhibit
craving of the stimulant nicotine, which is associated with intense
craving and is predicted to induce patterns of brain activation
that parallel those seen with psychostimulants such as cocaine.
[0006] Without being bound to any particular theory or mechanism,
D1-like agonists (also referred to herein as "D1-like receptor
agonists") are thought to provide some or all of the sensations of
rush and high associated with the use of a psychostimulant or
nicotine, without leading to significant levels of further drug
craving. Although a patient treated with a D1-like agonist may
consume an initial quantity of a psychostimulant or nicotine,
further craving of the addictive drug will be inhibited, thereby
inhibiting binge-like drug consumption. D1-like antagonists are
thought to inhibit initial cravings for psychostimulants or
nicotine or to reduce the euphoria felt from psychostimulants or
nicotine, thereby inhibiting the initiation of binge-like
behavior.
[0007] Accordingly, the invention features a method for inhibiting
a psychostimulant-induced craving in a human, which method entails
identifying the human as being psychostimulant-dependent, and
administering to the human a D1-like antagonist or D1-like agonist
in an amount effective to inhibit craving of the psychostimulant.
In various embodiments, the psychostimulant may be cocaine
(including crack cocaine) or amphetamine.
[0008] In a related method, the invention features a method for
inhibiting a nicotine-induced craving in a human, which method
entails identifying the human as being nicotine-dependent, and
administering to the human a D1-like antagonist or D1-like agonist
in an amount effective to inhibit craving of nicotine (e.g.,
craving of nicotine-containing cigarettes). Typically, in
practicing the methods of the invention, the patient (i.e., human)
is a compulsive user of the psychostimulant or nicotine. The
methods of the invention are particularly useful in inhibiting
drug-induced craving, which is the craving experienced after drug
use (e.g., within 15 seconds to 120 minutes).
[0009] Now that, as shown by the experiments described below, the
psychostimulant-induced patterns of brain activation in humans and
rodents are known to overlap each other closely, rodents (e.g.,
rats and mice (including knockout mice, such as knockouts of the D1
receptor or DAT transporter)) can be used as animal model systems
for measuring the ability of a test compound to inhibit
psychostimulant-induced or nicotine-induced craving in a human.
This method of the invention entails administering the test
compound to a rodent; administering a psychostimulant or nicotine
to the rodent; and measuring an attenuation in the level of brain
activation in the rodent subsequent to administration of (a) the
test compound and (b) the psychostimulant or nicotine, as compared
with the level of brain activation obtained upon (a) administration
of the psychostimulant or nicotine to the rodent without (b)
administration of the test compound, as a measure of the ability of
the test compound to inhibit psychostimulant-induced or
nicotine-induced craving in a human. In various embodiments, the
psychostimulant can be cocaine (including crack cocaine) or
amphetamine. The animal may be drug-naive, or it may be chronically
addicted to a psychostimulant or nicotine by virtue of its having
been repeatedly treated with the drug previously. Useful animal
models of chronic addiction include, without limitation, (a)
animals taught to self-administer drugs and (b) condition-place
preference paradigms (where the readiness of an animal to go to a
place where the animal has previously had the drug is measured).
The test compound can be a known D1-like agonist or D1-like
antagonist (such as those described herein), or it may be any
compound of interest, such as uncharacterized small organic
molecules of interest. The test compound typically is administered
at a dosage of 0.0001 to 100 mg/kg of the body weight of the
rodent. Typically, the test compound is administered to the animal
0 minutes to 2 days (e.g., 15 minutes to 8 hours) prior to
administration of the psychostimulant or nicotine to the animal.
The test compound can be administered to the animal in a single
dose or in repeated doses (e.g., 1, 2, or 5 or more times daily)
prior to administration of the psychostimulant or nicotine. The
decrease in the level of brain activation can be measured by any of
the various methods for measuring brain activations, such as
functional MRI (with or without contrast agents such as
monocrystalline iron oxide nanocolloid (MION) particles or
gadolinium) and laser Doppler-flowmetry, as described above for
example.
[0010] Examples of suitable D1-like antagonists for use in the
methods of the invention include SCH 39166; SCH 23390; A-69024;
bulbocapnine; butaclarnol HCl, (+)-; fluphenzanine HCl;
flupenthixol 2 HCl, cis-(Z)-, fluspirilene; haloperidol; SCH-12679;
SKF-83566; thioridazine HCl; thiothixine HCl; trifluoperazine 2HCl;
and trifluorperidol HCl. Examples of suitable D1-like agonists
include A-86929; 6-chloro-PB HBr, (.+-.)-(SKF 81297); SKF 38393;
A-69024, N-allylnorapomorphine HBr, R(-)-; apomorphine HCl, R(-)-;
6-bromo-APB HBr, r(+)-; 6-Chloro-APB HBr, (.+-.)-(SKF-82958);
Pergolide methanesulfonate, and SKF 77434. Such agonists or
antagonists can be administered to the patient or animal at a
dosage of 0.0001 mg/kg to 100 mg/kg of the body weight of the
patient or animal, and more typically at a dosage of 0.1 to 1.0
mg/kg of the body weight of the patient or animal. In a typical
method of administration, the D1-like antagonist or D1-like agonist
is administered to the patient or animal orally, intravenously, or
intramuscularly. Typically, an initial dosage of the D1-like
antagonist or D1-like agonist will be administered to the patient
within 0 to 24 hours of consumption of a psychostimulant or of
nicotine by the patient, and potentially continued with a daily
dose(s) for 1 to 365 days, or even life-long if desired.
[0011] A "psychostimulant" is any agent having antidepressant or
mood-elevating properties in a human, such as amphetamine and
cocaine, or producing reinforcing effects during drug
self-administration paradigms or conditioned-place preference
paradigms in non-human animals.
[0012] A "compulsive" psychostimulant or nicotine user is a person
who has an irresistible impulse or strong craving to use a
psychostimulant or nicotine, which typically is manifested as
repetitive self-administration of the psychostimulant or
nicotine.
[0013] A "D1-like agonist" is any compound that activates signal
transduction via D1-like dopamine receptors or D1 dopamine
receptors, typically by reversibly binding with its receptor and
often with the resultant effect that is proportional to the number
of receptors occupied. D1 agonists are encompassed by the term
D1-like agonists as used herein.
[0014] A "D1-like antagonist" is any compound that interacts with
D1-like or D1 dopamine receptors, or with other components of the
D1 effector mechanism, to inhibit the action of an agonist while
initiating no effect itself. D1 antagonists are encompassed by the
term D1-like antagonists as used herein.
[0015] "Craving" is a monofocused motivational state, which occurs
in the context of a perceived deficit of a reward. The degree of
craving can be measured in terms of the behavior the person is
willing to implement to get the objective of their motivational
state.
[0016] The invention offers several advantages. By providing a
method for inhibiting drug-induced craving, the invention provides
an effective method for treating drug addictions (e.g., cocaine
addiction). Because D1-like receptors are preferentially localized
to the regions of the brain that mediate drug-induced craving
(e.g., the nucleus accumbens and the amygdala), the use of D1-like
agonists and antagonists provide specificity in targeting the
appropriate regions of the brain. By using D1-like agonists in
treating a patient, the patient may experience some sensations that
are similar to those achieved through the use of the addictive drug
(e.g., rush and high), without experiencing the withdrawal-related
craving associated with cessation of drug use. The patient can
experience non-psychostimulant-induced euphoria and/or reward,
along with forming emotional memories of these experiences.
[0017] Other features and advantages of the invention will be
apparent from the following detailed description, and from the
claims. Unless otherwise defined, all technical and scientific
terms used herein have the same meaning as commonly understood by
one of ordinary skill in the art to which this invention belongs.
Although methods and materials similar or equivalent to those
described herein can be used in the practice or testing of the
present invention, suitable methods and materials are described
herein. All publications, patent applications, patents, and other
references mentioned herein are incorporated herein by reference in
their entirety. In the case of a conflict, the present
specification, including definitions, will control. In addition,
the materials, methods, and examples are illustrative and are not
intended to limit the scope of the invention, which is defined by
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic representation of the design of
experiments described herein. Over a 5 hour period, subjects
participated in 10 experimental fMRI scans. The experimental runs
were grouped, 5 apiece, around each of the double-blind infusions.
Physiological recording along with behavioral ratings were
initiated prior to the first flow-sensitive alternating inversion
recovery (FAIR) scan and continued through the second FAIR scan of
each infusion block. After the first infusion, the second
double-blind infusion could not be initiated until the 120 minute
blood sample had been collected. In between the sets of functional
scans for each infusion, clinical scans were acquired for
neuroradiological assessment. These scans included: sagital T1
images, axial proton density, and T2 images, and 3D time-of-flight
angiogram.
[0019] FIG. 2 is a graph of average behavioral ratings. The rush,
high, low and craving ratings were averaged within each category
for the 9 of 10 subjects who had interpretable cocaine fMRI data
after motion correction, and behavioral ratings time-locked to the
scanner.
[0020] FIG. 3 is a schematic summary of limbic and paralimbic brain
regions that correlate with euphoria as compared with those regions
that correlate with craving. Above these summary schematics is a
schematic of the brain regions predicted to be active after the
infusion of cocaine. Two other brainstem monoaminergic regions,
potentially encompassed in a pontine activation seen in the
baseline vs post-infusion comparison described herein are also
illustrated. This pontine activation correlated with behavioral
ratings for rush.
[0021] FIGS. 4A and 4B are graphs showing a dose dependent response
after cocaine infusion in frontal cortex measured with (FIG. 4A)
blood oxygen level dependent (BOLD) signal and (FIG. 4B) laser
Doppler-flowmetry (LDF). Data are presented as MEAN.+-.SEM for
(FIG. 4A) R.sub.2 detected in a 2.7 mm bilateral volume of frontal
cortex approximately 2 mm rostral to anterior commissure and 2 mm
lateral to midline and (FIG. 4B) percent cerebral blood flow (CBF)
measured by LDF in approximately the same region of frontal cortex
as in (FIG. 4A) in a separate set of rats. The sample size is
presented in parenthesis, and significant differences between pre-
and post-infusion signals (as determined by paired t-test) are
indicated as: *, P<0.02; **, p<0.05. Since no significant
response was detected either with saline controls or cocaine doses
.ltoreq.0.01 mg/kg, these values were combined.
[0022] FIG. 5A is a graph illustrating a temporal response of CBF,
cerebral blood volume (CBV), and BOLD signal after infusion of 0.5
mg/kg cocaine determined in approximately the same anatomical
region of frontal cortex. Data are presented as percent CBF
measured by LDF (n=6), percent CBV determined by MRI with
monocrystalline iron oxide nanocolloid (MION) contrast (n=4) (other
agents that have an effect on magnetic relaxation also can be
used), and R.sub.2 for BOLD (n=5). Cocaine was infused at Time=0
minutes. Responses in CBF, CBV and R.sub.2 were calculated relative
to the average value for the 5 minute baseline period (-5 to 0
minutes) immediately before cocaine infusion; time courses
represent average responses. Averaged baseline standard deviation
was .+-.1.9% for CBF; .+-.1.4% for CBV; .+-.0.15 for R.sub.2. FIG.
5B is a graph of representative temporal response in arterial blood
pressure due to infusion of 0.5 mg/kg cocaine for an individual
rat.
[0023] FIG. 6A is a representative map of regional CBV response in
rat after infusion of 0.5 mg/kg cocaine. Data are presented for 8
consecutive 1 mm thick coronal slices; the first slice is
approximately 2 mm rostral to anterior commissure. The percent
increase in CBV is depicted in light shades of grey (range 2%-33%)
overlying T2 weighted echo planar images. FIG. 6B is a series of T2
weighted echo planar images of slices used in FIG. 6A. The numbered
overlays depict regions of interest for time course analysis: 1.
AGm, agranular medial frontal cortex; 2. AGI, agranular lateral
frontal cortex; 3. MPFC, medial prefrontal cortex; 4. A Cing,
anterior cingulate cortex; 5. SS, somatosensory cortex; 6. Aud,
auditory cortex; 7. Vis, visual cortex; 8. D ST, dorsal striatum;
9. V St, ventral striatum; 10. N Ac, nucleus accumbens; 11. D Thal,
dorsal thalamus. FIG. 6C is a series of high resolution
conventional T2 weighted images of the same slices used in FIG.
6A.
[0024] FIGS. 7A-7D are graphs showing time dependent changes in CBV
within brain regions of interest after 0.5 mg/kg cocaine infusion.
Regions and abbreviations are as given in the description of FIG.
6B. Cocaine was infused at Time=0 minutes. Data represent average
percent changes in CBV (n=4) relative to a 5 minute baseline
obtained immediately before cocaine infusion.
[0025] FIGS. 8A and 8B are a series of images showing that
pretreatment by SCH-23390 blocked functional activation in rat
brain after 0.5 mg/kg cocaine infusion. Representative regional
maps of CBV increase are shown in 3 consecutive 1 mm thick coronal
slices of rat brain; the first slice is approximately at the level
of anterior commissure. The average percent increase in CBV is
depicted in light shades of grey (range 2%-33%) overlying T2
weighted echo planar images. For FIG. 8A, the rat received no
pretreatment; for FIG. 8B, the rat was pretreated with 0.1 mg/kg
SCH-23390 15 minutes before cocaine infusion.
[0026] FIG. 9 is a graph representing a time course of CBV response
in frontal neocortex (circles) and dorsal striatum (triangles)
after 0.5 mg/kg cocaine infusion in rats either pretreated with 0.1
mg/kg SCH-23390 (closed circle and closed triangles) or without
pretreatment (open circles and open triangles). In both animals,
cocaine infusion was initiated at Time=0; the pretreated rat
received SCH-23390 15 minutes before cocaine infusion (Time=-15).
Responses were calculated relative to the average CBV during the 5
minute baseline period immediately preceding drug infusion (-5 to 0
minutes in the non-pretreated animal and -20 to -15 minutes in the
SCH-23390 pretreated animal).
DETAILED DESCRIPTION
[0027] The invention provides methods for inhibiting in a human a
psychostimulant-induced or nicotine-induced craving for additional
psychostimulants or nicotine. By inhibiting such a drug-induced
craving, the binge-like behavior typically associated with the use
of addictive drugs (e.g., cocaine, amphetamine, or nicotine) can be
inhibited. Preferred candidates for treatment in accordance with
the invention are patients who are psychostimulant-dependent or
nicotine-dependent. Generally, the typical patient is susceptible
to, or suffering from, a psychostimulant-induced or
nicotine-induced craving; such patients can be identified simply on
the basis of their having consumed a psychostimulant or nicotine in
the 30 seconds to 120 minutes prior to administration of a D1-like
agonist or antagonist to the patient. Typically, the patient is a
compulsive user of a psychostimulant or of nicotine. In an
alternative method, the pattern of brain activation in the patient
(as determined, for example, by fMRI as described herein) indicates
that the patient is suffering from a craving induced by a
psychostimulant or nicotine (e.g., sustained signal maxima in the
nucleus accumbens and negative signal changes in the amygdala).
[0028] Once a patient is identified as being
psychostimulant-dependent or nicotine-dependent (and therefore
susceptible to, or suffering from, a psychostimulant-induced or
nicotine-induced craving), a D1-like antagonist or D1-like agonist
is administered to the patient in an amount effective to inhibit
the craving. Examples of suitable D1-like antagonists include,
without limitation, SCH 39166; SCH 23390; SCH 23388; A-69024;
bulbocapnine; butaclamol HCl, (+)-; fluphenzanine HCl;
fluphenthixol 2 HCl, cis-(Z)-, fluspirilene; haloperidol;
SCH-12679; SKF-83566; thioridazine HCl; thiothixine HCl;
trifluoperazine 2HCl; and trifluorperidol HCl. Examples of suitable
D1-like agonists include A-86929; 6-chloro-PB HBr, (.+-.)-(SKF
81297); SKF 38393; A-69024, N-allylnorapomorphine HBr, R(-)-;
apomorphine HCl, R(-)-; 6-bromo-APB HBr, r(+)-; 6-Chloro-APB
HBr,(.+-.)-(SKF-82958); Pergolide methanesulfonate, and SKF 77434.
Other D1-like antagonists and D1-like agonists are known in the art
and can be used in practicing the invention. Such agonists and
antagonists, as well as additional suitable agonists and
antagonists, are available from commercial suppliers such as
Research Biochemicals International. Conventional methods can be
used to identify additional D1-like antagonists and D1-like
agonists, which also can be used in practicing the invention. If
desired, the D1-like antagonists and agonists can be used in
combination (e.g., at a ratio from 1:1 up to 10:1).
[0029] D1-like antagonists and D1-like agonists can be formulated
for administration to the patient by any of a variety of known
routes. For example, solid formulations of the D1-like antagonists
or D1-like agonists for oral administration may contain suitable
carriers or excipients, such as corn starch, gelatin, lactose,
acacia, sucrose, microcrystalline cellulose, kaolin, mannitol,
dicalcium phosphate, calcium carbonate, sodium chloride, or alginic
acid. Disintegrators that can be used include, without limitation,
micro-crystalline cellulose, corn starch, sodium starch glycolate
and alginic acid. Tablet binders that may be used include acacia,
methylcellulose, sodium carboxymethylcellulose,
polyvinylpyrrolidone (Povidone), hydroxypropyl methylcellulose,
sucrose, starch, and ethylcellulose. Lubricants that may be used
include magnesium stearates, stearic acid, silicone fluid, talc,
waxes, oils, and colloidal silica.
[0030] Liquid formulations of the D1-like antagonists or D1-like
agonists for oral administration prepared in water or other aqueous
vehicles may contain various suspending agents such as
methylcellulose, alginates, tragacanth, pectin, kelgin,
carrageenan, acacia, polyvinylpyrrolidone, and polyvinyl alcohol.
The liquid formulations may also include solutions, emulsions,
syrups and elixirs containing, together with the active
compound(s), wetting agents, sweeteners, and coloring and flavoring
agents. Various liquid and powder formulations can be prepared by
conventional methods for inhalation by the patient.
[0031] Injectable formulations of the D1-like agonists and D1-like
antagonists may contain various carriers such as vegetable oils,
dimethylacetamide, dimethylformamide, ethyl lactate, ethyl
carbonate, isopropyl myristate, ethanol, polyols (glycerol,
propylene glycol, liquid polyethylene glycol, and the like). For
intravenous injections, water soluble versions of the compounds may
be administered by the drip method, whereby a pharmaceutical
formulation containing the D1-like agonist or D1-like antagonist
and a physiologically acceptable excipient is infused into the
patient. Physiologically acceptable excipients include, for
example, 5% dextrose, 0.9% saline, Ringer's solution or other
suitable excipients. For intramuscular preparations, a sterile
formulation of a suitable soluble salt form of the agonist or
antagonist can be dissolved and administered in a pharmaceutical
excipient, such as Water-for-Injection, 0.9% saline, or 5% glucose
solution.
[0032] The optimal concentration of the D1-like antagonist or
D1-like agonist in each pharmaceutical formulation varies according
to the formulation itself. Typically, the pharmaceutical
formulation contains the agonist or antagonist at a concentration
of about 0.1 to 90% by weight (such as about 1-20% or 1-10%).
Appropriate dosages of the D1-like antagonist or D1-like agonist
can readily be determined by those of ordinary skill in the art of
medicine by assessing inhibition of drug-induced craving in the
patient, and increasing the dosage and/or frequency of treatment as
desired. The optimal amount of the D1-like antagonist or agonist
for inhibiting craving of a psychostimulant or nicotine may depend
upon the mode of administration, the age and the body weight of the
patient, and the condition of the patient; Typically, a D1-like
antagonist is administered at a dosage of 0.001 to 100 mg/kg of
body weight of the patient; e.g., the antagonist is administered at
a dosage of 0.1 to 1.0 mg/kg. A D1-like agonist typically is
administered at a dosage of 0.001 to 100 mg/kg of body weight of
the patient, e.g., at a dosage of 0.1 to 1.0 mg/kg.
[0033] In a typical method of treatment, the patient is a
compulsive user of a psychostimulant or nicotine. Treatment of an
addiction to a psychostimulant or nicotine thus generally involves
a regimen in which a D1-like antagonist or D1-like agonist is
repeatedly administered to the patient. Typically, the D1-like
antagonist or D1-like agonist is administered to the patient once
every two days, once daily, or even more frequently to alleviate
the drug dependency, and typically over a time span of about 1 to
12 months or even life-long if needed.
EXAMPLES
[0034] For the following examples, in vivo studies were conducted
with human cocaine users, and with rats that were treated with
cocaine. To identify the circuitry active in human brains during
cocaine infusions, and to associate this activity with subjective
reports for both cocaine-induced euphoria and post-cocaine craving,
functional Magnetic Resonance Imaging (fMRI; Kwong et al., 1992,
Proc. Natl. Acad. Sci. 89:5675-5679; Ogawa et al., 1992, Proc.
Natl. Acad. Sci. 89:5951-5955; Bandettini et al., 1992, Magn.
Reson. Med. 25:390-397) was used in conjunction with physiological
monitoring and online evaluation of computerized behavioral rating
scales. The fMRI data obtained from subsequent studies conducted
with rats, when compared with data obtained from humans, showed a
notable overlap in the pattern of cocaine-induced activation of
subcortical structures. In rats, cocaine-induced brain activation
was completely blocked by administration of the D1 antagonist
SCH-233390 prior to administration of cocaine. These studies
indicate that the D1 receptor mediates the acute action of cocaine,
and these studies support the conclusion that D1-like agonists and
D1-like antagonists can be used to inhibit craving of
psychostimulants, and of nicotine. These studies also show that an
animal model can be used to measure the ability of a test compound
to attenuate psychostimulant-induced or nicotine-induce brain
activations and thereby inhibit craving. An exemplary animal model
system is described below.
Example I
Human Studies
[0035] For the experiments with humans, cocaine-dependent
volunteers underwent an unblinded cocaine infusion the night before
the fMRI experiment for clinical screening, and for training with
behavioral assessments on scales of rush, high, low and craving.
During the subsequent double-blind cocaine (0.6 mg/kg) and saline
infusions, subjects rated these four scales every 15 seconds during
multiple fMRI acquisitions (FIG. 1). In these experiments, blood
oxygen level dependent (BOLD) signal changes (Ogawa et al., 1992,
Proc. Natl. Acad. Sci. 89:5951-5955) were measured after infusions
of cocaine and saline, separately, into patients. Briefly, the
following data show that infusion of cocaine induced BOLD signal
changes (i.e., "activations"), whereas few activations were
detected after infusion of saline. Following infusion of cocaine,
patients exhibited dynamic patterns of brain activation over time
as the patient experienced sensations of rush, high, low, and
drug-induced craving. A distinct pattern of brain activation is
exhibited as patients experienced drug-induced craving. The brain
regions exhibiting positive or negative activations during
drug-induced craving (the nucleus accumbens and amygdala in
particular) contain high levels of D1-like receptors. Compounds
that alter the function of these receptors in the nucleus accumbens
and/or amygdala (i.e., D1-like agonists and antagonists) can now be
used to inhibit drug-induced craving, and inhibit binge-like
consumption of addictive drugs such as psychostimulants and
nicotine.
[0036] 1. Clinical and Physiological Data
[0037] Seventeen subjects were infused with cocaine while being
scanned with fMRI. Scans affected by uncorrectable gross movement
were rejected as uninterpretable. Of these 17 subjects, 10 had
interpretable fMRI data for the cocaine infusions and 10 had
interpretable data for the saline infusions after motion-correction
(7 studies with usable matched infusions).
[0038] Following the cocaine infusion (0.6 mg/kg over 30 seconds),
there was an increase in heart rate (HR) within the first minute,
while the increase in mean blood pressure (MBP) was slower.
Similarly, the drop in end-tidal carbon dioxide (ETCO.sub.2) was
also slower. Cocaine (n=17) caused the HR to increase rapidly from
a pre-infusion value of 60.+-.7 beats per minute (bpm) to 79.+-.16
bpm at 2 minutes post-infusion (p<0.0001), to 82.+-.12 bpm at 5
minutes post infusion (p<1.times.10.sup.-6), to 93.+-.14 bpm at
10 minutes post infusion (p<1.times.10.sup.-8). Normal sinus
rhythm was observed in all subjects throughout the study.
[0039] The mean blood pressure rose slightly, from 96.+-.12 torr
before the infusion, to 101.+-.12 torr at 2 minutes post-infusion
(p<0.11, N.S.), then up to 111.+-.15 torr at 5 minutes
(p<0.002) before starting to slowly decline. The ETCO.sub.2
dropped slowly from a baseline of 39.+-.4 mm Hg to 36.+-.4 mm Hg by
10 minutes (p<0.02). In all subjects scanned, these three
measures had returned to baseline by 2 hours, the inter-infusion
interval (Gollub et al., 1996, Proc. Soc. Neuroscience 3:1933).
These physiologic responses to the 0.6 mg/kg cocaine infusion are
in close accord with previously published studies in experienced
cocaine abusers (Fischman et al., 1982, Fed. Proceed 41:241-246;
Fischman et al., 1985, J. Pharm. Exper. Ther. 235:677-682; Foltin
et al., 1991, J. Pharm. Exper. Ther. 257:247-261).
[0040] Plasma samples taken before the first infusion demonstrated
an absence of residual cocaine at the time of the first infusion in
all of the subjects studied. Peak plasma cocaine levels (Cmax)
following the cocaine infusion ranged from 197 to 893 mcg/L with a
mean of 388.7.+-.233.0 mcg/L (n=7 subjects with complete data). The
time to peak cocaine plasma concentration varied from 3 to 15
minutes for subjects in the initial series of experiments
(mean.+-.SD: 7.6.+-.4.2 min) and the 4 subjects with interpretable
re-test experiments (mean.+-.SD: 6.0.+-.2.9 min).
[0041] Scores for the Profile of Mood States (POMS) inventory,
assessed before, in-between, and after the two infusions, showed no
change in five of the six POMS measures (i.e., tension, depression,
vigor, fatigue, confusion) over the total scan time. Vigor
increased in the second infusion for both cocaine and saline
infusions. Spielberger scores assessed before, between, and after
both infusions indicated no significant change in anxiety levels
across scans. These observations are consistent with the
interpretation that subjects did not experience increased
discomfort or anxiety in the scanner environment over the course of
the experiment.
[0042] 2. Behavioral Measures
[0043] All 10 subjects with interpretable cocaine fMRI data
reported clear cocaine effects (see FIG. 2). Both the peak rush
(max score=3; mean.+-.SD=2.2.+-.1.1) and the peak high (2.1.+-.0.8)
occurred, on average, at 3 minutes post-infusion. The peak low
(primarily reports of dysphoria and paranoia: 0.9.+-.0.8) occurred
at 11 minutes post-infusion; while, peak craving (1.3.+-.0.9)
occurred at 12 minutes post-infusion. No subject reported effects
from the saline infusion on any of the four measures. The
behavioral ratings obtained for rush, high, low, and craving
measures at a cocaine dosage of 0.6 mg/kg (under blinded conditions
and given in the fMRI scanner) were higher than those obtained at a
dosage of 0.2 mg/kg (under unblinded conditions) (rush: 1.2.+-.1.1;
high: 1.7.+-.1.2; low: 0.8.+-.0.8; craving: 1.0.+-.1.3). For the
four subjects with interpretable test-retest cocaine data,
behavioral measures were unchanged on average for the two
conditions (retest results, rush: 1.8.+-.1.0; high: 2.3.+-.0.5;
low: 1.0.+-.0.8; craving: 1.0.+-.1.2).
[0044] 3. Cocaine Infusion
[0045] (a) Foci of Signal Change
[0046] As shown on Kolmogorov-Smirnov statistical maps, cocaine
caused regional signal changes in the brain
(p<7.1.times.10.sup.-6; see Tables 1-4 for multiple limbic and
paralimbic regions) in discrete foci in the nucleus
accumbens/subcallosal cortex (NAc/SCC), caudate nucleus, putamen,
basal forebrain, thalamus, insula, hippocampus, parahippocampal
region, cingulate, lateral frontal cortices, lateral temporal
cortex, parietal cortex, striate and extrastriate cortices.
Regional changes in signal were detected in the amygdala (see Table
4), temporal pole, and medial frontal cortex. Positive signal
change was also noted in the vicinity of the ventral tegmentum and
the pons.
[0047] For most of the positive and negative activations with
cocaine, plots of signal intensity versus time indicated that the
brain activations had early signal maxima, with a rapid (starting
within 1 minute of the signal maxima) decrease toward baseline.
Some of the brain activations, however, demonstrated early signal
maxima that were sustained at a plateau level for time periods
ranging from 5 minutes until the end of the scanning interval. As
described below, these differences in time course produced a
dynamic pattern of brain activation following infusion of cocaine;
positive and negative activations in various regions of the brain
were correlated with different behavioral states (e.g., rush, high,
low, and craving). To determine the extent to which the averaged
data reflects activations common to individual subjects in the
study, statistical maps were analyzed for 16 subcortical regions
(see FIG. 3 for examples of anatomic definitions, and Tables 1-4
for results) in the 10 subjects used for the average map. The data
are presented as the ratio of the number of subjects who showed
activation in that structure at a less stringent p-value threshold
(p<.0.001); (for a description of this type of analysis, see
Breiter et al., 1996, Arch. Gen. Psychiatry 53:595-606). The
individual data analysis strongly supports the average results in
the NAc/SCC, thalamus, hippocampus, insula, cingulate gyrus and
parahippocampal gyrus, with 8 or 9 of 10 subjects contributing to
the group activation. Other regions including caudate, putamen,
basal forebrain, and VT also reflected the majority activation,
with 6-8 subjects showing activation.
1TABLE 1 Characterization of cocaine effects on fMRI signal in
Subcortical Grey Structures Multiple % Signal Proportion
Correlation Tal Coordinates P-value Change Individuals Analysis
Anatomic Region R/L A/P S/I (KS-statistic) (Pre vs post drug) (p
< 0.001) Rush Craving NAc/SCC R 6 7 -9 7 .times. 10.sup.-6 1.5
9/10 + L -6 13 0 4 .times. 10.sup.-6 1.5 8/10 + Caudate R 13 -3 22
5 .times. 10.sup.-7 0.8 8/10 + - L -9 -3 19 3 .times. 10.sup.-7 1.0
7/10 + Putamen R 28 7 -3 4 .times. 10.sup.-8 1.4 8/10 + - L -28 7
-3 NS (5 .times. 10.sup.-5) 0.5 5/10 BF/GP R 22* 1* -6* NS 6/10 + L
-19 0 -3 6 .times. 10.sup.-9 1.8 7/10 + - Thalamus aThal R 3 -18 13
6 .times. 10.sup.-8 0.4 8/10 L NS 7/10 pThal R 6 -25 16 9 .times.
10.sup.-7 1.4 8/10 + L -6 -31* 9* NS 8/10 + LGN R 19 -25 0 NS (8
.times. 10.sup.-5) 0.8 8/10 + L -19 -25 -3 2 .times. 10.sup.-7 0.5
7/10 +
[0048]
2TABLE 2 Characterization of cocaine effects on fMRI signal in
Temporal Lobe Multiple % Signal Proportion Correlation Tal
Coordinates P-value Change Individuals Analysis Anatomic Region R/L
A/P S/I (KS-statistic) (Pre vs post drug) (p < 0.001) Rush
Craving Hippocampus aHIp R 28* -18* -9* NS 9/10 - L -28* -17* -16*
NS 10/10 +/- .gradient. pHIp R 34 -28 -13 2 .times. 10.sup.-8 1.8
9/10 + + L -22 -37 0 NS (1 .times. 10.sup.-5) 0.9 10/10 + Insula
aINS R 34 13 6 3 .times. 10.sup.-8 0.9 10/10 + L -28 19 -6 5
.times. 10.sup.-6 0.5 8/10 + pINS R 41 -15 0 2 .times. 10.sup.-9
1.1 8/10 + L -41 -12 -3 3 .times. 10.sup.-11 1.0 7/10 + + Amygdala
R 22 -6 -13 NS (-7 .times. 10.sup.-5) -1.2 4/10(+), 5/10(-) - L -25
-9 -19 -1 .times. 10.sup.-6 -0.3 3/10(+), 5/10(-) -
[0049]
3TABLE 3 Characterization of cocaine effects on fMRI signal in
Medial Paralimbic Cortices Multiple % Signal Proportion Correlation
Tal Coordinates P-value Change Individuals Analysis Anatomic Region
R/L A/P S/I (KS-statistic) (Pre vs post drug) (p < 0.001) Rush
Craving Cingulate G. aCG (BA 24/32) R 9 13 34 1 .times. 10.sup.-8
0.9 9/10 + (BA 32) R 3 26 28 3 .times. 10.sup.-7 0.8 + (BA 24) B 0
-3 31 3 .times. 10.sup.-8 1.0 9/10 + + pCG (BA 31) R 3 -31 38 3
.times. 10.sup.-6 0.5 8/10 + (BA 31) L -9 -28 41 NS (1 .times.
10.sup.-5) 0.5 5/10 + + Parahippocampal G. (BA 28) R 22 -21 -22 6
.times. 10.sup.-6 2.7 9/10 + + + (BA 28) L -19 -28 -9 2 .times.
10.sup.-8 0.5 9/10 + + (BA 35) R 16* -40* -6* NS + (BA 19) L -30*
-50* 2* NS + +
[0050]
4TABLE 4 Characterization of cocaine effects on fMRI signal in
Brainstem Multiple % Signal Proportion Correlation Tal Coordinates
P-value Change Individuals Analysis Anatomic Region R/L A/P S/I
(KS-statistic) (Pre vs post drug) (p < 0.001) Rush Craving VT
(SN) R 9 -15 -13 4 .times. 10.sup.-6 1.1 6/10 + L -6 -21 -6 3
.times. 10.sup.-9 1.5 6/10 +
[0051] Tables 1-4 summarize activation due to cocaine infusion.
`Anatomic Region` identifies the structure on the basis of
subcortical location, lobe, gyrus (if medial paralimbic cortex), or
placement in the brainstem. `BA` indicates the probable Brodmann
area, for cortical areas, of activation in the group average data
as determined from the atlas of Talairach and Tournoux (1988).
Activation laterality is denoted by R and L; when bilateral, a B is
used. `Tal Coordinates` denotes the Talairach coordinates using the
atlas of Talairach and Tournoux (1988) of the voxel with the
maximum p-value for the KS maps of pre- vs post-infusion time
points, and overlapping correlation regions (except where denoted
by a *, in which case the coordinates denote the location of the
voxel with maximum p-value for the correlational analysis when no
significant activation was present in the KS maps of the group
average data). Coordinates are expressed in mm from the anterior
commissure: R/L, right(+)/left(-); A/P, anterior(+)/posterior(-);
S/I, superior(+)/inferior(-). `P-value` indicates the maximum
p-value for each activated cluster of voxels on the unsmoothed
Kolmogorov-Smirnov statistical map. Regions are listed as
significant if p<7.1.times.10.sup.-6. When `NS` (nonsignificant)
is followed by a p-value in parentheses, this indicates a region of
activation which did not meet the significance threshold, yet due
to symmetric placement with respect to another activation in the
opposite hemisphere was included. Percent signal change was
determined for each activation by taking all voxels around the max
vox with p<10.sup.-5 and comparing the first 38 fMRI time points
with the subsequent 98 time points. `Proportion Individuals` lists
the number of subjects to the total number of subjects (N=10) who
showed activation (p<10.sup.-3 for each voxel) in each
anatomically defined region of interest; these regions of interest
may include one or more activations from the group average
statistical analysis. `Correlation Analysis` lists the results of a
multiple correlational analysis of the fMRI time data to the
behavioral measures of rush and craving. A `+` indicates a positive
correlation, a `-` indicates a negative correlation, and a `.o
slashed.` indicates no correlation to the measure. To be tabulated,
a correlation region had to have 5 voxels with R>0.70 for each
voxel. The symbol indicates two nearby correlation regions of
opposite sign in the same anatomic region. In Table 3, two `+`
signs are placed in the craving column for one activation; in this
case, one correlation region was correlated to similar degree with
both rush and craving measures, while the other correlation region
was uniquely correlated to craving alone.
[0052] (b) Correlation Maps
[0053] Multiple correlation analysis was used to show that the
patterns of brain activations observed following cocaine infusion
were associated with specific behavioral states. More specifically,
this analysis was used to show that early, but sustained,
activations in the nucleus accumbens/subcallosal cortex and
amygdala are correlated with cocaine-induced craving, rather than
cocaine-induced rush. A correlation value (R) for each behavioral
measure was calculated in order to describe the strength of
similarity between the signal time course of each brain voxel
(i.e., volume element in the fMRI scan) and a particular behavioral
measure (e.g., rush, high, low, or craving). Such a correlation
between patterns of brain activation and behavioral measures is
readily seen between the rush and the craving ratings, which are
the most temporally distinct from each other (see FIG. 2).
[0054] While rush ratings had early and transient maxima, craving
ratings have a longer latency before reaching maximum. The
resulting correlation data are summarized in Tables 1-4. Regions of
the brain activation that correlated with rush had early and
transient signal maxima. Strong correlations were noted for the
left basal forebrain and bilateral VT. In addition, many other
regions of brain activation on the maps were positively correlated
with rush ratings, including sections of the right cingulate gyrus,
bilateral insula, bilateral thalamus, bilateral caudate nucleus,
bilateral pontine brainstem, and the majority of activations in the
prefrontal cortex.
[0055] Regions that showed a significant correlation with craving
had early signal maxima (or minima for the negative activations),
followed by sustained signal change. The sustained signal change in
these regions produced a strong correlation with craving. Thus,
while the NAc/SCC and amygdala showed early signal changes
(positive and negative changes), at the time of rush and high, both
regions showed persistent signal changes that correlated
significantly with reports of craving but not rush. Another region
which showed a positive correlation with craving was a region of
the right parahippocampal gyrus.
[0056] Other regions of the brain demonstrated a significant
correlation with both rush and craving ratings; these regions are
identified in Tables 1-4 by a `+` symbol in the columns for both
ratings. Of these regions, those that overlapped with activations
seen in the comparison of preinfusion versus postinfusion time
points include sections of the left parahippocampal gyrus, left
cingulate gyrus, left insula, and right hippocampus.
[0057] .COPYRGT. Test/Retest Comparisons
[0058] To confirm the brain activation results described above,
seven subjects were retested by infusing cocaine into the patients
at times ranging from 3.5 to 4 months after the first experiment.
Of these seven subjects, data for four of the subjects was
interpretable after infusion of cocaine infusion and motion
correction. These four subjects received their double-blind cocaine
and saline infusions in the same order for the retest experiments
as for the test experiments described above. To keep expectancies
as similar as possible between test and retest conditions, subjects
were informed on several occasions that the identity of the first
retest infusion did not imply the identity of the second retest
infusion, and that a double-blind experimental design was
maintained for subjects and researchers during all retest
infusions. Regions of signal change that were similar between the
average brain maps following the test and retest cocaine infusions
are listed in Table 5. Regions of brain activation that overlapped
had statistical maxima that were within 1.5 cm of each other, or
the two activation clusters had overlapping voxels at a high
statistical threshold. Twenty-six of thirty-two post-cocaine
activations in the test sample were matched by similar activations
in the retest experiments, including subcortical regions originally
hypothesized to be activated, namely the NAc/SCC, basal forebrain,
and caudate. For regions such as the NAc/SCC, the percent signal
change for voxels meeting the threshold of p<10.sup.-5 in the
test condition (Left=3.8%, Right=2.4%) was marginally higher than
the percent signal change for the retest condition (Left=2.3%,
Right=2.1%), though more voxels met the p<10.sup.-5 threshold on
retest. Other areas of activation that matched between test and
retest conditions included parahippocampal, thalamic, insular, and
cingulate regions.
5TABLE 5 Test-Retest Cocaine Infusions: Regions of Similarity for
Foci of Positive Signal Change TEST RETEST Anatomy Tal Coordinate
Vx Anatomy Tal Coordinate Vx Proximity (Region/BA) R/L A/P S/I #
(Region/BA) R/L A/P S/I # (<1.5 cm) Subcortical Grey Structures
Caudate/ 25 -27 18 8 Caudate 18 -12 21 77 - NAc Caudate/ 9 15 -3 81
GO a11 3 15 -6 160 + NAc BF/GP -21 0 -6 10 BF/GP -15 3 0 23 +
Thalamus/ 6 -27 12 62 Caudate 18 -12 21 77 - pThal Cingulate a23 3
-27 28 43 - Temperal Lobe Lateral and Intrasylvian Surfaces GTm a21
43 -6 -15 28 GTm a21 46 -18 -9 26 + .psi. Insula 37 -15 -3 38 +
Insula -40 -15 -6 129 Insula -40 -9 0 63 + GTm a21 -46 -24 -3 57 +
Insula -40 6 0 45 Insula -40 -9 0 63 + Insula -34 12 18 12 Insula
-37 18 6 66 + .psi. Medial Paralimbic Cortices Cingulate a24 0 -3
40 8 Cingulate a24 3 9 34 83 + Cingulate a23/ 21 -27 34 13
Cingulate a23 12 -18 34 18 + 31 Cingulate a23 3 -27 28 43 - Parahip
a35 18 -36 -12 89 GF a37 46 -51 -21 152 - GF a20/ 34 -33 -15 26 +
.psi. 36 Parahip a28/ -21 -24 -21 83 Thalamus/ -18 -15 3 17 - 36
pThal Parahip a35/ -28 -27 -15 150 + 36
[0059] Table 5 shows which activations were similar between test
and retest conditions for the cocaine infusions. Specific anatomic
regions are described using the nomenclature discussed above with
the exception of the following terms: GTm (Gyrus temporalis
medius), GF (Gyrus Fusiformis), GO (Gyrus Orbitales). `BA`
indicates the probable Brodman area, for cortical areas, of
activation. Under `Coordinates` are the Talairach coordinates
(Talairach et al., 1988, New York: Thieme Medical Publishers) of
the voxel with the maximum p-value as determined from the KS maps
(Breiter et al., 1996, Arch. Gen. Psychiatry 53:595-606).
`Coordinates` are expressed in mm from the anterior commissure:
R/L, right(+)/left(-); A/P, anterior(+)/posterior(-); S/I,
superior(+)/inferior(-). The number of voxels around the max vox
which meet the p-value threshold of p<10.sup.-6 are listed under
`Vox #`. `Proximity` lists whether the voxels with the maximum
p-values for each activation are within 1.5 cm of each other; thus
a `+` is placed in the last column if they are <1.5 cm apart, or
a `-` is placed there if they are more than 1.5 cm apart. If there
is no overlap, but the max vox of the two activations are within
1.5 cm of each other, the symbol is also placed in the last
column.
[0060] 4. Saline Infusion
[0061] (a) Foci of Signal Change
[0062] As a control, saline was infused into the 10 patients in the
initial test group, and fMRI was used to measure brain activations.
Saline infusions produced no signal change in the limbic or
paralimbic regions. One focus of signal change was noted in the
left temporal pole, which approximated a similar activation for the
cocaine infusion. For areas outside of the limbic and paralimbic
regions, signal changes were noted in the inferior frontal gyrus,
inferior/middle temporal gyri, and extrastriate region, and signal
changes were noted in the lateral frontal cortex, superior temporal
gyri, and extrastriate cortex. Six activations with saline matched
the location of activations seen in the cocaine maps.
[0063] (b) Test/Retest Comparisons
[0064] As with the cocaine test/retest comparisons, four of seven
subjects had interpretable saline infusion data for test-retest
comparison after motion-correction. For the saline test-retest
comparison with 4 individuals, no limbic or paralimbic regions were
activated. For regions outside of limbic and paralimbic regions,
six of the test activations were also similar to those seen during
the retest. Of these six activations, four activations approximated
activations seen with the average saline map of ten individuals,
suggesting that the subgroup of four represent a good approximation
of the group of ten.
[0065] The saline retest indicated that there were several new
activations not detected during the first saline test, the majority
of which (10/16) were in the striate, extrastriate, and ventral
temporal cortex. Eleven of the sixteen activations were similar to
activations seen with the initial cocaine infusion for the total
cohort and the retest cocaine infusions in the subgroup of 4
individuals (Table 5). On the basis of location of activation
maxima, 11 of the 16 new activations seen during the saline retest
infusion in the NAc/SCC, the frontal cortex, and the temporal
cortex were seen with either the cocaine test or retest infusions.
The activations likely represent a common effect from expectation
of cocaine.
[0066] Summary of Human Studies
[0067] Following an infusion of cocaine under double-blind
conditions, subjects reported early maximal behavioral ratings for
rush and high at .about.3 minutes after cocaine infusion. The
maximal ratings for craving and low were reported to occur at 11-12
minutes after cocaine infusion. Cocaine plasma concentrations
reached maximum at .about.7 minutes after infusion.
[0068] Euphoria (Rush): Brain regions that showed focal increases
in blood oxygen level dependent signals at the time of onset of
euphoria included the NAc/SCC, basal forebrain, and ventral
tegmentum, caudate, putamen, thalamus, medial temporal and
paralimbic regions (hippocampus, parahippocampal gyrus, cingulate
cortex, and insula), brainstem (pons), and neocortical regions,
such as the lateral prefrontal cortex, lateral temporal cortex,
parietal cortex, and occipital cortex. Changes in fMRI signal were
also noted in the amygdala, temporal pole, and medial frontal
cortex. In comparison to cocaine, saline produced few regions of
fMRI signal changes, which were limited to the lateral prefrontal
and temporo-occipital cortex. Small regions of signal change were
also noted in the lateral prefrontal cortex and temporal
cortex.
[0069] Multiple correlational analysis of the averaged behavioral
ratings with the averaged cocaine fMRI data indicated differences
in the temporal pattern of activation, which can be associated with
rush and with craving ratings (FIG. 3). Brain activation correlated
with rush ratings was noted in the ventral tegmentum, left basal
forebrain, midbrain and pontine brainstem, bilateral caudate
nucleus, and right cingulate gyrus. Other brain activations that
showed a similar pattern of early and transient signal maxima,
included regions of prefrontal, parietal, temporal, and occipital
cortex.
[0070] Craving: Brain activation that was highly correlated with
craving measures was noted in the NAc/SCC and right
parahippocampus. A strong correlation with craving was also noted
in the amygdala, a region which also showed a significant fMRI
signal change on the average brain map. The detection of sustained
signal change in the NAc/SCC explains its stronger association with
craving, than with rush, ratings. In general, the differences at
high thresholds between the rush and craving correlation maps
reflect a distinction between behavioral ratings with early peaks
and shorter duration (i.e., rush) and ratings with prolonged time
courses (i.e., craving). It is significant that subtraction of fMRI
time courses with early maxima and short duration from those with
prolonged time courses would produce a time course closely
resembling that of the craving ratings. This suggests a model for
cocaine-induced craving in humans. Craving may not be mediated by
one or two distinct brain regions; rather, post-cocaine craving
reflects a change over time in the pattern of brain activation from
cocaine. Many brain regions are active at the time that subjects
report euphoria. Over time, however, only a few brain regions
remain activated; this change in the pattern of brain regions
activated is associated with the subjective experience of
cocaine-induced craving.
[0071] Use of D1-like Agonists and Antagonists: As is explained in
greater detail above, craving for psychostimulants, such as cocaine
and amphetamine, and stimulants such as nicotine, can be inhibited
by administering to a patient a D1-like antagonist or D1-like
agonist. This conclusion is founded, at least in part, on four
observations, three of which show tight homology between animal and
human data on the brain circuitry involved with reward, cocaine
effects on dopamine neurotransmission for producing reward, and the
distribution of dopamine receptor subtypes (e.g., the D1 receptor)
in the brain. The fourth observation relates to animal data showing
that drugs specific to D1 receptors alter reward processes in the
brain.
[0072] Based on investigations using rodent and primate models, the
mesoaccumbens dopamine pathway, extending from the ventral
tegmentum of the midbrain (VT) to the nucleus accumbens, appears to
be the critical shared substrate of the reinforcing effects of
cocaine and other addictive drugs. Using non-drug stimuli, the
nucleus accumbens has also been shown to play a critical role in
learning associated with reinforcement.
[0073] Behavioral research with animal models has implicated
increased dopamine transmission in the NAc with behavioral
responses to rewards. The exact relationship of mesoaccumbens
dopamine function to the action of a reward as an incentive or as a
reinforcement has been an area of controversy. The implicit
assumption to the general view of dopamine transmission in the NAc
is that dopamine transmission is a central correlate of the
reinforcing actions of rewards. It is important to note that
incentive-based reward has to do with expectancies and conditioned
memories that alter future behavior or lead to adaptations of
behavior. Craving in humans is a form of learned expectancy, while
experiences such as cocaine-induced rush represent an acutely
reinforcing effect.
[0074] Prior to the research described above, the "brain reward"
circuitry was never observed in humans, nor proven to be involved
with the rewarding effects of drugs such as cocaine. The research
described herein allowed the localization of brain reward circuitry
in the human in association with both reinforcement-based reward
and incentive-based reward. Regarding incentive-based reward, this
work demonstrated that a distinct pattern of brain activation is
exhibited in humans during periods of craving induced by the
psychostimulant cocaine. Using fMRI, which measures blood flow
oxygenation changes associated with changes in neuronal activity,
these studies showed that psychostimulant-induced craving (e.g.,
cocaine-induced craving) is correlated with early, but sustained
signal maxima in the nucleus accumbens and the amygdala. This
observation contrasted with the observation that fMRI activation in
the basal forebrain and VT was correlated with rush. Together,
these observations in humans represent the first time that
circuitry found active in animals during reinforcement reward and
during incentive reward has been found to function in a similar
manner in humans.
[0075] The data described herein show homology between animal and
human reward circuitry, it is also intriguing that the
psychostimulant cocaine produces its rewarding effects in animals
and humans via the same mechanism. Namely, reinforcement reward in
animals depends on the change in synaptic dopamine levels in the
mesoaccumbens circuit produced by cocaine-like drugs via blockade
of the dopamine reuptake transporter (DAT). This change in synaptic
dopamine levels leads to greater receptor occupancy at
post-synaptic dopamine receptors. In both animals and humans, the
acutely reinforcing effects of psychostimulant drugs can produce a
pattern of repeated self-administration.
[0076] A third domain involved with brain reward and
stimulant-induced euphoria in which animals and humans are similar
is that of the distribution of dopamine receptor subtypes. In
particular, the D1 receptor has been found in significant amounts
in the nucleus accumbens and the amygdala of humans.
[0077] In animals, it has been shown that drugs that are D1
antagonists produce significant alterations of drug-related
expectancies. Specifically, they are potent inhibitors of stimulant
cues, alter expectancies for conditioned preferences, and can
inhibit the reinforcing effects of psychostimulants such as
cocaine. In one study, the alteration of expectancies for
conditioned preferences in rodents was strongly associated with D1
antagonist effects in the nucleus accumbens. Accordingly, one
treatment of cocaine addiction, in accordance with the invention,
involves D1-antagonists, which alter function in the nucleus
accumbens and/or amygdala reducing reinforcement reward, and
.COPYRGT. distribution of D1 receptors, D1-antagonists can be used
to reduce expectancies in general (experienced as cue-induced or
cocaine-induced craving in the human), and D1-agonists can be used
to reduce cocaine-primed expectancies in humans and therefore be an
effective form of treatment in humans. These methods of treatment
are now possible because of the research described above, showing
(a) that humans have the same extended neural network of reward
circuitry as animals, and (b) that this circuitry performs both
reinforcement reward and incentive reward function (e.g., for
craving).
[0078] Experimental Procedures Used for Human Studies
[0079] A detailed description of the experimental procedures
utilized in the above study follows.
[0080] Subjects
[0081] Of the 17 subjects who completed the experimental protocol,
13 were men and 4 were women [mean age=34.5.+-.4.6 years;
education=12.2.+-.1.6 years; weight=79.6.+-.17.8 kg; Addiction
Severity Index (McLellan et al., 1980, Journal Of Nervous and
Mental Disorders 168:26-33) Composite Score (0 to 1.00) on the Drug
dimension=0.18.+-.0.13, and on the Alcohol dimension=0.27.+-.0.25;
Hamilton Anxiety Scale (0 to 54) 2.94.+-.2.08; Hamilton Depression
Scale (0 to 52) 7.53.+-.5.66]. All subjects were right-handed.
Except for cocaine addiction, they were medically and
neurologically normal by physical exam, review of systems, blood
work including electrolytes, liver function tests, cell blood
count, and toxicology. No subject had a history of head trauma with
loss of consciousness, or had any family history of sudden cardiac
death or cardiac disease. All subjects tested negative for human
immunodeficiency virus (HIV). Women were not pregnant by HCG
testing, and were scanned at the midfollicular phase of their
menstrual cycle. All subjects fulfilled criteria for cocaine
dependence, with or without comorbid alcohol or marihuana abuse, by
Mini-Structured Clinical Interview for DSM-IV (SCID) (American
Psychiatric Association, 1994, Washington, D.C.: American
Psychiatric Assoc. 4th ed. rev.). The subjects were selected to be
heavy, long-term cocaine users (mean=7.8.+-.6.0 years; days of
cocaine use in 30 days prior to experiment=16.2.+-.8.2 days). The
monetary expenditure for cocaine was $397.0.+-.318.0 over the week
prior to the experiment. No subjects were seeking or receiving
treatment for substance abuse at the time of the study. To be
accepted into the imaging protocol, during screening, subjects had
to have one positive urinalysis to confirm recent cocaine use, but
had to be abstinent from cocaine and alcohol for at least 18 hours
before the infusion. Approximately 18 hours before each imaging
session, subjects underwent a screening IV test-dose of 0.2 mg/kg
in the Massachusetts General Hospital (MGH) Mallinckrodt General
Clinical Research Center (GCRC) under the supervision of a
cardiologist and psychiatrist, to ascertain cardiac and
neurological tolerance of the experimental procedures. They were
subsequently monitored in the GCRC until the time of scanning. All
subjects gave informed consent to participate in these procedures
following the rules of the Subcommittee on Human Studies at
MGH.
[0082] Experimental Design
[0083] Subjects were admitted to the MGH GCRC for the screening
procedures; those meeting all criteria were boarded overnight on
the unit in preparation for imaging the following day. The
following morning the subject had bilateral intravenous catheters
placed (right forearm for cocaine or saline infusion, left forearm
for serial venous blood sampling for quantitative cocaine levels).
Scanning was performed between 11AM and 3PM during which the
subject was in the scanner for two periods of time each lasting
from 45 to 90 minutes. During each scanning period, one infusion
was given, either cocaine (0.6 mg/kg, maximum dose 40 mg) or saline
(both in a volume of 10 cc given over 30 seconds IV) in a
randomized, double blind order. Five different scans were performed
during each period. The infusion itself was made 5 minutes into an
18 minute long blood oxygen level dependent (BOLD) scan. The BOLD
infusion scan was bracketed by flow-sensitive alternating inversion
recovery (FAIR) and visual stimulation BOLD scans (the data from
these scans were used to delineate the global vs. regional signal
changes from cocaine). The time interval between functional scans
within a period was kept to a minimum. The entire sequence of 5
functional scans was completed within 45-60 minutes. The subject
was removed from the scanner for a 15-30 minute rest and then was
returned to magnet and the sequence was repeated for the second
infusion. A minimum of two hours had to pass between each
double-blind infusion.
[0084] Subject Instructions
[0085] For the pre-experiment test-infusion with 0.2 mg/kg cocaine
on the night before scanning, subjects were informed they would
receive a small dose of intravenous cocaine in the presence of a
cardiologist and a psychiatrist to screen for medical side-effects
from intravenous cocaine, and to train them in making behavioral
ratings of their experience.
[0086] For experiments performed in the magnet, subjects were
informed they would receive two infusions to which both they and
the experimenters were blind. Infusions could either be saline or
0.6 mg/kg of cocaine in saline; the experience of one infusion did
not imply what would be the identity of the other. Subjects were
further asked to continue behavioral ratings throughout the FAIR
and BOLD infusion scans (.about.40 minutes in total), and to remain
as motionless as possible to minimize fMRI movement artifacts.
[0087] Plasma/Urine Monitoring
[0088] Sequential 4 ml venous blood samples were collected
immediately before and at 1, 3, 5, 10, 15, 30, 60, 90 and 120
minutes following each infusion. The 120 minute sample for the
first infusion was also the pre-infusion sample for the second
infusion.
[0089] Physiological Monitoring
[0090] Physiologic monitoring was conducted using an InVivo
OmniTrak 3100 patient monitoring system (Orlando, Fla.) modified to
permit on-line computer acquisition of physiologic measurements.
Each subject was fitted with chest leads to record the
electrocardiogram (ECG) and to measure heart rate (HR), a nasal
cannula to measure respiratory rate and end-expiratory carbon
dioxide (ETCO.sub.2), and a blood pressure cuff to measure
non-invasively systemic mean blood pressure (MBP). The temporal
resolution of the system for sampling blood pressure was once every
two minutes. The InVivo system sampled and displayed updated values
for each of the other parameters once per second, except for the
ECG trace which was digitized at a rate of 100 Hz.
[0091] The measured physiologic parameters were ported to a
Macintosh Power PC 7100 running a custom National Instruments
LabView data acquisition program. This program allowed the
simultaneous acquisition of 1) the digitized analog ECG trace
signal acquired using a National Instruments MIO16L board, 2) the
GE scanner J8 trigger pulse which indicated when the gradient coils
of the magnet were firing and 3) serial port read of ASCII
characters reporting physiologic measures from the InVivo
system.
[0092] Precautions taken to ensure safe conduct of the study
included use of ACLS trained personnel, frequent running of mock
codes with clocked performance of tasks and strict definition of
individual tasks, and presence of a cardiologist at the time of all
infusions whose sole responsibility was to monitor subject safety.
Before and after completion of both infusions, subjects underwent a
12-lead ECG to determine the absence of any interval change from
the experiments. Because of magnetohydrodynamic effects on the ECG
tracing, a baseline rhythm strip was obtained prior to each drug
infusion and all subsequent tracings were compared to that one.
[0093] Behavioral Monitoring
[0094] For both infusions, analog scales for behavioral response
were projected via the LabView program and a back projection
television system (Sharp Liquid Crystal, RU2000) outside the
Faraday shield of the scanner. These projected stimuli were then
focused via a biconvex lens (Buhl Optical) inside the Faraday
shield onto a rear-projection screen which was viewed through an
overhead mirror in the magnet bore. For both infusions, subjects
viewed images prior to actual experimentation so that images could
be focused and centered in each subject's visual field.
[0095] During FAIR and BOLD infusion scans, behavioral measures of
rush, high, low, and craving were obtained in a continuous sequence
each minute. Thus, over each 15 second epoch, one rating scale
would be projected for the subject's response. Given four scales,
it took one minute to cycle through the complete set of scales.
Timing of scan initiation, infusion onset and offset, and scan
completion were linked with ongoing behavioral reports to allow
subsequent correlational analysis between behavioral ratings and
fMRI acquisitions. Behavioral responses were acquired with a
four-button button-press which had been adapted to the magnet
environment by construction with non-magnetic components and
filtering of its output at the Faraday shield.
[0096] To obtain meaningful behavioral ratings during scanning,
subjects were trained beforehand. The day before scanning, subjects
were interviewed in depth by one of two board-certified
psychiatrists to fully describe their experience of cocaine intake.
These descriptions were then categorized by the psychiatrist and
subject into four components: the rush, high, low, and craving
which were to be rated on an integer scale of 0 (none) to 3
(maximum). The individualized conventions for description of
subjective responses were then tested, during the unblinded
pre-infusion with 0.2 mg/kg cocaine, on a portable computer with a
program simulating that used in the MRI.
[0097] Of the four behavioral measures, only craving was defined
operationally in terms of the action the individual wanted to
engage in (to get more cocaine). The other three behavioral
measures, rush, high, and low, were defined in terms of subjective
feelings which were not necessarily associated with a behavioral
output, or associated with the planning and implementation of
physical activity. Thus, by definition, only craving was defined as
a motivational state. In general, rush experiences involved
physical sensations of elevated heart rate and sweating, along with
internal feelings variously characterized as `speeding` sensations
and sensations of `being out-of-control`. In contrast, the high
experience was generally associated with feelings of
self-confidence, well-being, and sociability. The low experience
encompassed all negative subjective feelings potentially associated
with cocaine use such as anxiety, paranoia, dysphoria, or
anhedonia; the majority of subjects in this study discussed the low
in terms of dysphoric affect distinct from a diminishment in the
high experience.
[0098] Imaging
[0099] Scanning was performed with a quadrature head-coil and a 1.5
T MR scanner (General Electric) modified for echo-planar imaging
(Advanced NMR). Imaging involved the following protocol. First, a
sagittal localizer scan [conventional T1-weighted spoiled gradient
refocused gradient echo (SPGR) sequence; through-plane
resolution=2.8 mm; 60 slices] was performed to orient, for
subsequent scans, 15 contiguous axial slices covering the whole
brain. This scan was also used as the structural scan for Talairach
transformation. Next, an automated shimming technique was used to
optimize B.sub.0 homogeneity (Reese et al., 1995, J. Magn. Reson.
Imaging 5:739-745). This was followed by a SPGR T1-weighted
flow-compensated scan (resolution=1.6 mm.times.1.6 mm.times.8 mm)
scan, which was primarily obtained to aid Talairach transformation
during data analysis (see Breiter et al., 1996, Arch. Gen.
Psychiatry 53:595-606). The fourth scan was a T1-weighted echo
planar inversion recovery sequence (TI=1200 msec, in-plane
resolution=1.57 mm) for high-resolution structural images to be
used in preliminary statistical maps, but not with Talairach
transformed or averaged maps. Finally, BOLD imaging was performed
using an asymmetric spin echo T2*-weighted sequence (TR=8000,
TE=50, 180 refocusing pulse offset by -25 ms; FOV=40.times.20 cm;
in-plane resolution=3.125 mm; through-plane resolution=8 mm; 15
contiguous axial slices covering the whole brain) to measure
`activation` (local changes in blood flow and oxygenation) (Kwong
et al., 1992, Proc. Natl. Acad. Sci. 89:5675-5679; Ogawa et al.,
1992, Proc. Natl. Acad. Sci. 89:5957-5955; Bandettini et al., 1992,
Magn. Reson. Med. 25:390-397). Images were acquired interleaved for
136 time points for each infusion.
[0100] Data Analysis
[0101] Plasma/Urine Levels: Cocaine quantitative assays were
performed by the MGH Clinical Chemistry Laboratory using a liquid
chromatography with photodiode array detection method they
developed (Puopolo et al., 1992, Clin. Chem. 38:1838-1842), with
minor modifications (flow rate increased from 2.0 to 2.6 ml/minute
and LCPCN column length increased from 150 to 250 mm). Intra-assay
imprecision at 100, 20, and 10 mg/L for cocaine is 5.1%, 5.7% and
6.6% respectively.
[0102] Physiological Data: The data analysis and graphing program
IGOR (WaveMetrics, Inc.) was used to analyze the data. Data were
first analyzed by a 2 way ANOVA with drug treatment (saline,
cocaine) and time of measurement as factors. When significant F
values were obtained for one of the physiologic measures,
individual time points were compared by post-hoc t-tests to
determine if (and at what times) the change from baseline was
significant. The Bonferroni correction for multiple comparisons was
used; the criteria for significance at the 0.05 level was
p<0.007.
[0103] Behavioral Data: The integer output for each behavioral
rating was segregated by category of rush, high, low, and craving.
For the group data in FIG. 2, the 18 measures for each behavioral
category obtained during the 18 minute BOLD infusion scan were
averaged for the 9 subjects with both interpretable behavioral data
and fMRI data. This averaged data was then utilized in the
correlational analysis of the cocaine fMRI data.
[0104] BOLD Data for Initial fMRI Experiments, and for Test/Retest
Experiments:
[0105] Motion correction: To reduce head motion, each subject was
positioned using a bitebar, and echo-planar data was motion
corrected using an algorithm (Jiang et al., 1995, Hum. Brain Mapp.
3:1-12) adapted from Woods et al (1992), and described elsewhere
(Breiter et al., 1996, Arch. Gen. Psychiatry 53:595-606). Motion
correction of the BOLD saline infusion data revealed an average
maximal displacement of 1.8.+-.2.3 mm resulting in a mean
correction per time-point of 0.6.+-.0.5 mm. For the cocaine
infusion data, there was an average maximal displacement of
1.1.+-.0.7 mm resulting in a mean correction per time-point of
0.6.+-.0.4 mm. After motion correction, time-series data were
inspected to assure that no data set evidenced residual motion in
the form of cortical rim or ventricular artifacts >1 voxel.
There was no statistically significant difference in maximal
displacement between paired groups of saline vs. cocaine infusions
(p<0.4).
[0106] Talairach transformation: Each individual's set of infusion
related functional images, along with the associated conventional
structural scans, were transformed into Talairach space (Talairach
et al., 1988, New York: Thieme Medical Publishers; Breiter et al.,
1996, Arch. Gen. Psychiatry 53:595-606; Breiter et al., 1996,
Neuron 17:875-887) and resliced in the coronal orientation over 57
slices with isotropic voxel dimensions (x,y,z=3.125 mm). Because of
possible movement between acquisitions of structural and functional
scans, functional data were further fit to the structural scan by
translation of exterior contours. For the cocaine and saline
infusions, 2 subjects evidenced movement between structural and
functional scans of >2 voxels in magnitude, and, therefore, were
discarded from further analysis.
[0107] Normalization, Averaging & Concatenation: For cocaine
and saline infusions, Talairach-transformed functional data were
intensity scaled (i.e., normalized relative to a standard
pre-infusion epoch) so that all mean baseline raw magnetic
resonance signals were equal. Talairach-transformed structural and
functional data were then averaged by run across the 10 subjects
with interpretable cocaine infusion data, and the 10 subjects with
interpretable saline infusion data; similar averaging of
Talairach-transformed structural and functional data was performed
for the four subjects used in the test/retest analysis (Breiter et
al., [Abst] 1995, Proc. Soc. Magn. Reson./Euro. Soc. Magn. Reson.
Med. Biol. Joint Meeting 3:1348; Breiter et al., [Abst] 1995, Proc.
Soc. Neuroscience 3:1988; Breiter et al., 1996, Arch. Gen.
Psychiatry 53:595-606; Breiter et al., 1996, Neuron
17:875-887).
[0108] Voxel-by-voxel statistical mapping: Unsmoothed
Kolmogorov-Smirnov (KS) statistical images were constructed
(Breiter et al., 1996, Arch. Gen. Psychiatry 53:595-606; Breiter et
al., 1996, Neuron 17:875-887) from these averaged data sets
comparing baseline (N=38 time points) and post-infusion (N=98 time
points) epochs. Drift correction (i.e., removal of a first order
linear function) was incorporated in the statistical calculation,
but not for the signal intensity time courses shown. Subsequently,
clusters of activation were determined on data which was smoothed
by a 0.7 pixel gaussian filter (.about.Hamming filter in the
spatial domain). To guide the determination of activation clusters,
smoothed data sets were subjected to a cluster-growing algorithm
(Jiang et al., [Abst] 1996, Acad. Press 3(3):S67; Bush et al.,
[Abst] 1996, Acad. Press 3(3):S55), and activation clusters listed
which met a corrected p-value threshold. The cluster growing
algorithm was set to select activations with maximum p-values below
p<10.sup.-5, and to separate activations with pixels of
p<10.sup.-4 between them. All activation clusters were then
evaluated on the unsmoothed data to ascertain that they met cluster
constraints, did not overlap areas of susceptibility, had time
courses consistent with the experimental paradigm, and could be
anatomically localized (see below for details). The correction for
multiple comparisons of this data, in order to maintain an overall
<0.05, was the Bonferroni correction for all gray matter voxels
sampled in the brain, or p<7.1.times.10.sup.-6 (Breiter et al.,
1996, Neuron 17:875-887). To be tabulated, activations had to meet
cluster constraints on the unsmoothed KS statistical maps as
follows: (a) for subcortical gray matter, three contiguous voxels
with one voxel at p<7.1.times.10.sup.-6, and two voxels at
p<10.sup.-5; and (b) for cortical activations, five contiguous
voxels with one voxel at p<7.1.times.10.sup.-6, and four voxels
at p<10.sup.-5. The effect of such cluster constraints on
statistical significance has been discussed previously (Breiter et
al., 1996, Arch. Gen. Psychiatry 53:595-606).
[0109] The time-course of signal change was evaluated for each
putative activation identified on statistical maps of averaged data
by the cluster-growing algorithm. These signal intensity versus
time curves were assessed to ascertain that activation did not
precede infusion onset. All activations had to meet these two
criteria, along with anatomical constraints that the Talairach
coordinate of their maximum voxel (i.e., the voxel with the lowest
p-value) was in the brain as assessed by the Talairach atlas
(Talairach et al., 1988, New York: Thieme Medical Publishers), and
that the activation, when thresholded at p<10.sup.-5, did not
extend outside the brain when superimposed over the
Talairach-transformed structural images.
[0110] Neuroanatomical Analysis: A combined approach to anatomic
localization of functional data was used. The group average data
(GAD) was mapped using an approach focused on Talairach
coordinates. In addition, the individual data (ID) were mapped
using a region of interest based approach, focused on the limbic
and paralimbic areas.
[0111] Anatomic Localization of GAD: Statistical maps of group
averaged data were superimposed over high-resolution conventional
T.sub.1-weighted images which had been transformed into the
Talairach domain and averaged. Primary anatomic localization of
activation foci was performed by inspection of these coronally
resliced T1-weighted scans and via the Talairach coordinates of the
maximum voxel from each activation cluster (see section on
determination of activation clusters). Subcortical localization of
activations followed the region of interest conventions described
below. All activations were checked against the functional image
data to ascertain that they did not overlap areas of susceptibility
artifact. Such overlap was determined by whether or not a voxel's
signal intensity during the baseline was less than the average
voxel in its slice by 50% of the difference between the average
voxel signal intensity in the slice and the average voxel signal
intensity outside of the slice.
[0112] Anatomic Localization of ID: To assess the degree to which
subcortical activations seen in the group represent common
activations across the population, as opposed to the effect of
strong activations in a few subjects, each individuals Talairach
transformed T1 high resolution scan was inspected and regions of
interest (ROIs) defined. Visual inspection of the superimposed KS
statistical maps, thresholded at a liberal statistical threshold
(KS, p<0.001), was then performed to determine if activation was
present in each of the anatomic structures discussed below. These
results were tabulated as a ratio of individuals showing
lateralized activation in that structure to the total number of
subjects evaluated (N=10). As the predictions involved only
subcortical structures, the individual analysis also focused on
noncortical regions, with the exception of medial paralimbic and
intrasylvian cortices.
[0113] The methods used for definition of the subcortical ROIs
followed the conventions of the MGH Center for Morphometric
Analysis. These ROIs were defined by use of specific anatomic
landmarks identified by direct visualization of each individual
Talairach transformed T1 anatomic scan. These coronal scans had
voxel dimensions of x,y,z=3.125 mm, a matrix of
49.times.37.times.57, and were viewed on the computer monitor with
a size of 38 mm.times.31 mm size. Key landmarks necessary for
anatomic localization included: the anterior commissure (AC),
posterior commissure (PC), lateral geniculate nucleus (LGN),
mammillary body (MB), substantia nigra (SN), anterior and posterior
extents of amygdala, anterior and posterior extents of hippocampus,
posterior extent of pulvinar, collateral sulcus and splenium of
corpus callosum.
[0114] Sixteen ROIs were defined to encompass the following
structures: the caudate nucleus (Cau), the nucleus accumbens and
subcallosal cortex (NAc/SCC), the putamen (Put), the pallidum (GP),
the amygdala (Amy), the anterior and posterior insula (aINS and
pINS), the anterior and posterior hippocampus (aHIP and pHIP), the
parahippocampal gyrus (Parahip), the precommissural and
postcommissural cingulate gyrus (aCG and pCG), the basal forebrain
(BF), the precommissural and postcommissural thalamus (aThal and
pThal), the lateral geniculate nucleus (LGN), and the ventral
tegmentum (VT: including SN and surrounding region). Definitions
for each of these ROIs were as follows: Cau extents reached from
the anterior tip of its head to the part of its body corresponding
at the coronal level of the LGN. NAc/SCC was identified at the
inferior junction between the head of Cau and the Put. It was
delimited superiorly by a line connecting the inferior corner of
the lateral ventricle and the inferior most point of the internal
capsule abutting NAc/SCC and laterally by a vertical line passing
from the latter point. Put, GP, VT, LGN, and Amy were directly
visualized, and the posterior extent of Amy was at the identical
coronal plane as the anterior tip of aHip. The posterior extent of
the aHip was the coronal plane in front of the PC; the PC plane was
the anterior border of pHip. The posterior border of the pHip was
identified by direct visualization. Parahip was limited superiorly
by the hippocampus or the amygdala and inferiorly by the collateral
sulcus. By convention, Parahip activation behind the posterior end
of the hippocampus was not considered. The insula was directly
identified on the coronal plane throughout its anteroposterior
extent; its anterior portion (aINS) continued to the coronal plane
before the AC while its posterior extent (pINS) included the
coronal plane with the AC. The precommissural cingulate (aCG)
extended from the paracingulate sulcus anteriorly to the coronal
plane anterior to the posterior commissure. Its sperior border was
determined by the paracingulate sulcus through the coronal slice
containing the AC and, behind this plane, the cingulate sulcus. Its
inferior border was defined by the paracingulate sulcus (curving
portion) anteriorly, and the callosal sulcus posteriorly. The
postcommissural cingulate (pCG) extended from the coronal plane of
the PC anteriorly, to the subparietal sulcus posteriorly. Its
superior border was defined by the cingulate sulcus and the
subparietal sulcus, whereas, its inferior border was the anterior
portion of the calcarine sulcus (Damasio, 1995, Oxford U. Press;
Caviness et al., 1996, J. Cog. Neurosci. 8:566-587). BsFor region
extended anterioposteriorly from the NAc level to the SN coronal
section, and medially to the hypothalamus (which extended
anteroposteriorly from AC to include posteriorly the MB, having a
vertical line at the level of the optic tract or the lateral most
extent of the optic chiasm of the internal capsule as its lateral
border and the interhemispheric midline as its medial border). The
thalamus was divided anteroposteriorly in two sectors. The aThal
extended from the anterior tip of the thalamus to the coronal plane
anterior to the posterior commissure, and pThal extended posterior
to the PC, including the PC coronal section. The thalamic ROIs were
defined inferiorly by the hypothalamic fissure.
[0115] Correlational Analysis of BOLD Data from the fMRI
Experiments:
[0116] A multiple correlational analysis was performed between
group-averaged behavioral data (N=9), and group-averaged fMRI data
(N=10). In one subject, the behavioral data was not time-locked to
the scanner due to computer malfunction, thus these data were not
used in the group-average of behavioral data. The multiple
correlation technique involved (a) cross-correlation of the group
average behavioral ratings for rush and craving with the group
average fMRI data to generate correlation co-efficient (R-value)
maps, and (b) transformation of the R-value maps via the Fischer
transform into p-value maps. To be tabulated, an activation had to
have 5 contiguous voxels with R>0.70 for each voxel. For 136
time points, an R>0.70 corresponds to a p<10.sup.-20. Because
10 subjects were averaged, this R>0.70 corresponds to an
R>0.22 in the individual. The resultant maps illustrated the
brain regions whose signal change resembled the time course of
rating change for each category of subjective rating.
[0117] Comparison of BOLD Data from Test Experiments with Retest
Experiments:
[0118] For the subgroups of subjects which had interpretable repeat
cocaine infusion scan data (N=4) and those with interpretable
repeat saline infusion scan data (N=4), data analysis involving
Talairach transformation, signal normalization, averaging, and
statistical mapping followed the procedures described above. Also,
as above, activations were determined using the same
cluster-growing algorithm; activations were interrogated regarding
proximity to susceptibility, relationship to experimental paradigm,
and anatomy in similar manner. Activations were tabulated with the
number of unsmoothed voxels in each activation cluster which met
the criteria of p<10.sup.-6. Similarity of activation between
test and retest conditions was determined by the proximity of the
maximum voxels (i.e., with reference to p-value threshold) for each
activation, and by overlap between the set of voxels in each
cluster which met the threshold of p<10.sup.-6 (note: the
Bonferroni threshold for multiple comparisons is
p<7.1.times.10.sup.-6). To be considered "similar" activations,
they had to have their maximum voxels within 1.5 cm of each other,
or have at least one overlapping voxel at the strict p<10.sup.-6
threshold.
Example II
Animal Studies
[0119] In the following example, a drug-naive rat model was used to
identify the anatomical and temporal pattern of brain activation
induced by cocaine. Chronic drug use animal models can be used in a
similar fashion. As in the human studies described above, BOLD fMRI
in this drug-naive rat model was used to map cocaine-induced brain
activation. In addition, cocaine-induced activation of cerebral
blood flow (CBF) was mapped using laser Doppler-flowmetry, and
cocaine-induced activation of cerebral blood volume (CBV) was
mapped using MRI after injection of the contrast agent
monocrystalline iron oxide nanocolloid (MION). A dose-dependent,
region-specific activation of cortical and subcortical structures
was detected, and was particularly evident in regions with
significant dopaminergic innervation. In addition, these data show
a close temporal coupling of BOLD contrast CBF and CBV in frontal
cortex during activation. Similarly, both the dose response and the
anatomic extent of cortical activation determined with BOLD signal
agreed well with the regional specificity of increased CBF and
CBV.
[0120] Experimental Procedures Used for Animal Studies
[0121] A detailed description of the experimental procedures
utilized in the animal studies follows.
[0122] Animal Preparation
[0123] All procedures were carried out in accordance with NIH
guidelines. Male Harlan Sprague-Dawley rats (225-300 gm) were
anesthetized briefly with 1.5% halothane in oxygen for insertion of
left femoral arterial and venous cannulae and placement of
tracheostomy for mechanical ventilation (using a 16 gauge
intravenous catheter, Inste-W, Becton Dickinson, Sandy, Utah). All
wounds were infiltrated with 1% lidocaine before incision.
Following surgery, the inspired halothane concentration was reduced
to 0.7% and rats were paralyzed with 2 mg/kg intravenous
pancuronium, followed by a continuous intravenous infusion of
pancuronium at 2 mg/kg/hr. Pancuronium was dissolved in normal
saline administered at 5 ml/kg/hr. Rats were mechanically
ventilated (in a small animal volume controlled ventilator, Harvard
Apparatus, Inc., South Natick, Mass.) with a 80/20 air/oxygen
mixture, an inspiratory to expiratory ratio of 1:1, and an initial
tidal volume of 3.0 ml at a rate of 40 breaths per minute.
Ventilation parameters were adjusted to maintain normal arterial
blood gases (pH=7.40.+-.0.01, PaCO.sub.2=40.+-.2,
PaO.sub.2=145.+-.10). Arterial blood samples (150 .mu.l) withdrawn
from the arterial cannula were analyzed for arterial partial
pressures of oxygen, carbon dioxide, and pH (Ciba-Corning Model
1304) before administration of drugs, and at the end of each
experiment before sacrifice, to ensure animal stability. Arterial
blood pressure and rectal temperature were monitored throughout the
experiment. Only animals that exhibited stable physiological
parameters were induced for analysis. Rats torsos were wrapped in
two heating blankets (Gaymar, Orchid Park, N.Y.) circulating warm
water to maintain core temperature at 37-38.degree. C. To minimize
MRI motion artifact, rats were placed into a custom plastic cradle
attached to a head frame machined from deirin plastic (David Kopf
Instruments, Fremont, Calif.); heads were fixed with plastic screws
inserted into the ear canals and a bar inserted under the front
incisors. Rat heads were shaved and covered with gel toothpaste to
reduce magnetic susceptibility artifacts arising from air-tissue
interfaces; ear canals and oropharynx were also filled with
toothpaste. A surface coil was secured over the dorsal surface of
the head before positioning the animal in the magnet center.
Cocaine (RBI, Natick, Mass.), SCH-23390 (RBI, Natick, Mass.), and
cocaine methiodide (NIDA, Bethesda, Md.) were dissolved in normal
saline and administered in a 0.5 ml volume at a rate of 1 ml/min
via the femoral vein. Sixty minutes passed before injections of
cocaine were repeated.
[0124] Magnetic Resonance Imaging and Analysis
[0125] A 30 mm transmit and receive linear radio frequency surface
coil was used in all studies for brain water excitation and
detection. Prior to functional imaging, a multislice set of high
resolution conventional T.sub.2-weighted coronal rat brain images
was used to localize the anterior commissure. Functional MRI
studies employed multislice gradient echo planar imaging of 8-16
contiguous coronal rat brain slices of 1 mm thickness with the
first slice approximately 2 mm rostral to the anterior commissure;
typical voxel resolution was 0.6 mm.sup.3 at 1 mm slice thickness.
Images were acquired with gradient echo times of 25 ms and
repetition time of 5 sec; 2 averages were acquired for each time
point (10 sec temporal resolution).
[0126] BOLD fMRI studies were conducted at a magnetic field
strength of 4.7 Tesla (Omega Spectrometer, General Electric NMR
Instruments, Fremont, Calif.). To remove echo time (Te) dependence
and create a quantity that approximately reflects deoxyhemoglobin
concentration, BOLD signal (S) was converted to transverse
relaxation rate (.DELTA. R.sub.2* as .DELTA.
R.sub.2*=-ln{S(t)/S(0)}/T.sub.E (Ogawa, et al., 1993, Magn. Reson.
Med. 29:205-210; Ogawa, et al., 1993, 12th Annual Scientific
Meeting SMRM, pp. 618; and Ogawa, et al., 1993, Biophys. J.
64:803-812).
[0127] All CBV-weighted fMRI studies were performed at a field
strength of 2 Tesla (SISCO spectrometer, Varian Spectroscopic
Instruments, Palo Alto, Calif.). To obtain MRI signal that was
highly weighted by CBV, a mono-crystalline iron oxide nanocolloid
(MION) was injected at an iron dose of 12 mg/kg. MION was
synthesized using previously described techniques (Shen, et al.,
Magn. Reson. Med. 29:599-604 and Mandeville, et al., 1997, Magn.
Reson. Med. 37:885-890); the biodistribution (Schaffer, et al.,
1993, Magn. Reson. Imag. 11:411-417) and physicochemical properties
(Shen, et al., Magn. Reson. Med. 29:599-604; Jung, et al., 1996,
Int. Soc. Magn. Reson. Med., 4th Annual Meeting, pp. 1681) have
been reported. The blood half life of MION is approximately 4 hours
in rats (Jung, et al., 1996, Int. Soc. Magn. Reson. Med., 4th
Annual Meeting, pp. 1681); brain transverse relaxation rate
following injection of unlabeled MION shows no detectable change
for three hours after equilibration in the blood (Mandeville, et
al., 1997, Magn. Reson. Med. 37:885-890). Percent change in CBV was
calculated by assuming a linear relationship between the local
blood volume fraction (V) and the change in relaxation rate
(calculated as described above) after MION injection as: 1 V ( t )
V ( 0 ) = R 2 * ( t ) R 2 * ( 0 ) - 1.
[0128] Using this technique, hypercapnia-induced changes in CBV
compare well with similar determinations made by position emission
tomography (PET) and x-ray computed tomography (Zaharchuk, et al.,
1997, Magn. Reson. Med. 37: 170-175; Mandeville, et al., 1998,
Magn. Reson. Med. 39:615-624; and Payen, et al., 1998,
Anesthesiology 88:984992).
[0129] Region of interest (ROI) analyses were applied to the time
series for both BOLD and CBV weighted images. To generate a dose
response relationship, a 2.7 mm.sup.3 volume of bilateral frontal
cortex, approximately 2 mm anterior and 2 mm lateral to bregma, was
selected from both rCBV and BOLD image sets. BOLD R.sub.2* and
relative change in CBV were calculated by comparison of the average
signal during the 5 min pre-drug baseline with the signal from 1 to
11 minutes after infusion of cocaine. Similarly, in order to
identify brain regions in which there was significant change in
fMRI signal, each voxel in the image was subjected to a Student's
group t-test to determine the statistical significance of signal
change between a 5 min pre-drug baseline and 1 to 11 minutes after
the drug infusion. Maps were generated for BOLD and CBV image
series for both positive and negative signal change.
[0130] Laser Doppler-Flowmetry
[0131] Regional cortical blood flow was determined by LDF (Perimed,
PF2B, Stockholm, Sweden) as described previously (Ayata, et al.,
1996, J. Cereb. Blood Flow Metab., 16:539-541). Rats (n=8) were
prepared exactly as for dynamic MR studies and positioned in a
standard stereotaxic head frame. With the scalp incised and
retracted, two holes (1-2 mm in diameter) were drilled through the
skull 2 mm lateral to midline; one hole was 2 mm anterior to bregma
overlying frontal cortex, and the other was 8 mm posterior to
bregma to examine occipital cortex. The flow probe was positioned
directly upon exposed dura mater in a puddle of mineral oil. The
location overlying frontal cortex corresponded to the region of
interest for BOLD and CBV fMRI analysis. A 12 kHz band with a
sampling rate of 40 Hz was used; data were resampled at 5 Hz for
analysis. All data were collected, stored, and analyzed using
MacLab/8 data acquisition and analysis system (ADInstruments,
Mountain View, Calif.). Arterial pressure was continuously
monitored and the data stored; heart rate was calculated from
arterial pressure pulses by the data acquisition software. To
convert LDF signal to the percentage change in CBF following
cocaine infusion, LDF signal was normalized to the 5 minute period
immediately preceding the start of drug infusion; the offset of LDF
signal at zero flow was set as the signal remaining after death by
asphyxiation.
[0132] Results of Animal Studies
[0133] Dose Response
[0134] Acute intravenous cocaine infusion increased blood oxygen
level dependent (BOLD) signal in rat frontal cortex. FIG. 4A
illustrates the dose dependence of the response detected in frontal
cortex approximately at the level of the anterior commissure. The
increase in BOLD contrast (-R.sub.2) was calculated by comparing
the average signal before cocaine infusion with the average signal
during the period one to eleven minutes after injection of drug.
Cocaine produced a significant change in BOLD signal at doses of
0.5 mg/kg (p<0.02) and 1.0 mg/kg (p<0.05) as measured with a
paired t-test. A maximal R.sub.2 of 2.5.+-.0.6 sec.sup.-1 was
measured at 1 mg/kg, while little or no change in R.sub.2 was seen
below 0.1 mg/kg. At doses above 5 mg/kg, the response was
associated with profound hypotension and cardiac arrhythmia.
[0135] The enhanced BOLD signal was verified as corresponding to
increased blood flow by measuring CBF and LDF in approximately the
same region of frontal cortex as examined with BOLD fMRI. As shown
in FIG. 4B, CBF response to cocaine infusion closely paralleled
BOLD response. CBF increased significantly after 0.5, 1.0, and 5
mg/kg (p<0.02, paired t-test) with little or no change below 0.1
mg/kg. The maximum elevation of frontal cortex blood flow was
35.+-.3 after 1 mg/kg cocaine.
[0136] Temporal Response
[0137] The CBF response as measured by LDF in frontal cortex was
similar for BOLD and CBV contrast determined by dynamic MRI. Time
dependent changes in CBF, CBV, and BOLD contrast induced by cocaine
are shown in FIG. 5. Both cortical CBF and CBV rose sharply after
drug infusion and peaked at a maximum increase of 41% and 32% over
baseline, respectively, within approximately 3.5 minutes. CBF and
CBV returned to baseline by 25 minutes post infusion. BOLD contrast
followed a similar time course; peak R.sub.2 occurred at 4 minutes
and returned to baseline 20 minutes after infusion. The temporal
response of BOLD contrast, CBV, and CBF did not differ
significantly between 0.5 and 1.0 mg/kg cocaine.
[0138] Cocaine infusion was associated with a transient and small
(5-10 mm Hg) increase in arterial blood pressure which resolved
before changes in BOLD, CBF, or CBV were detected (FIG. 5B). A
bolus infusion of cocaine methiodide, a positively charged
quaternary cocaine derivative which does not cross the blood brain
barrier (Schindler, et al, 1992, Eur. J. Pharmacol. 213:99-105 and
Hemby, et al., 1994, J. Cereb. Blood Flow Metab. 9:323-328) at
doses of 1, 5, 10, and 20 mg/kg produced a transient decrease in
both blood pressure and heart rate, but did not produce any
significant change in frontal cortex CBF (data not shown),
indicating that the changes in fMRI signal observed with cocaine
are a direct consequence of cocaine-induced regional alteration in
brain activity and are not due to systemic effects of cocaine or a
global effect on cerebral vasculature.
[0139] Regional Specificity of Response
[0140] Since CBV-weighted fMRI significantly improves functional
sensitivity relative to BOLD fMRI (Mandeville, et al., 1998, Magn.
Reson. Med. 39:615-624), this technique was used to map the
regional activation pattern induced by cocaine infusion. A typical
cocaine activation map produced using MION contrast is shown in
FIG. 6. Acute cocaine infusion increased CBV in multiple regions,
with the largest increase in frontal cortex. Regional variations in
CBV were detected in the forebrain with gradients of rostral
greater than caudal, and medial greater than lateral CBV signal
identified in cortex. Activation of subcortical structures was also
evident with discrete regional increases within ventral and
dorsolateral striatum, nucleus accumbens, and dorsal thalamus. No
significant changes in CBV were detected in cerebellum,
hippocampus, hypothalamus, midbrain tegmentum, medulla, or pons
(p>0.05 compared to pre-drug baseline in all regions).
[0141] Regional brain activation detected with BOLD contrast agreed
closely within the region-specific increases in CBV after cocaine.
The largest magnitude R.sub.2 was observed in frontal neocortex;
R.sub.2 was smaller in lateral and occipital cortex. BOLD signal
changes were seldom apparent in subcortical structures including
striatum and thalamus, a result which presumably reflects the
reduced sensitivity of that technique relative to CBV-weighted
fMRI. No significant decrease in BOLD signal was apparent in any
parenchymal region after cocaine infusion. Large increases in BOLD
signal were observed in large venous structures, including sinuses
(sagital, transverse and straight) and the plexus of vessels
surrounding thalamus. Excluding large venous artifacts, the pattern
of detectable BOLD signal changes was consistent with the regional
activation pattern produced using CBV contrast.
[0142] Because cocaine stimulates dopaminergic neuronal
transmission within brain, the magnitude and duration of changes in
CBV after 0.5 mg/kg cocaine infusion was examined in eleven brain
regions including forebrain sites with rich (e.g., frontal cortex)
and sparse (e.g., occipital cortex) dopamine innervation (FIG. 6B).
As the CBV map indicates, cocaine infusion produced the greatest
activation and frontal cortical regions (FIGS. 7A & 7B);
agranular medial and agranular lateral frontal neocortex exhibited
the largest increases in CBV at peak, approximately 40% and 30%,
respectively. The magnitude of response was smaller in more lateral
and occipital neocortical regions including somatosensory,
auditory, and visual cortex. These results were consistent with
BOLD and LDF data. No significant change in CBF was detected by LDF
in the occipital pole even after infusion of 5 mg/kg cocaine.
Similarly, when the same region of interest analysis was applied to
images obtained with BOLD contrast, the magnitude of R.sub.2 was
less in occipital and lateral cortex when compared to frontal
cortex.
[0143] The magnitude of the CBV response was significantly larger
in cortical versus subcortical structures. The average response of
the four subcortical regions examined (dorsal and ventral striatum,
nucleus accumbens and dorsal thalamus) was only 45% as large as the
five frontal and parietal cortical regions (p<0.005, group
t-test). The time course, however, was similar in all cortical and
subcortical regions; maximum CBV change was achieved within 3-6
minutes after initiation of cocaine infusion and returned to
baseline over the succeeding 20 minutes.
[0144] D1 Receptor Mechanism
[0145] Pretreatment of rats with either 0.1 or 0.5 mg/kg SCH-23390,
a selective D1 receptor antagonist, 15 minutes before infusion of
0.5 mg/kg cocaine completely blocked cocaine-induced increases in
CBV (FIG. 8), although a small, transient decrease in CBV was
observed in both frontal neocortex and dorsal striatum (FIG. 9).
CBV reached nadir within 2 minutes post cocaine infusion with a 5%
and 8% drop in frontal neocortex and striatum, respectively.
Administration of SCH-23390 alone produced a small, region specific
decrease in CBV in a distribution of structures similar to that in
which CBV increased after infusion of cocaine without SCH-23390
pretreatment.
[0146] Results obtained using LDF in frontal cortex were consistent
with the CBV-fMRI data. SCH-23390 (0.5 mg/kg) blocked
cocaine-induced CBF activation in frontal cortex for all measured
cocaine doses up to 5 mg/kg. Furthermore, 0.5 mg/kg cocaine
infusion following pretreatment with SCH-23390 produced a small
decrease in CBF of -18.+-.3% (n=3, p<0.04, paired t-test)
relative to the pre-drug baseline. These data show that
cocaine-induced brain activations are mediated by the D1 receptor,
suggesting that D1-like agonists and D1-like antagonists can be
used to inhibit psychostimulant-induced and nicotine-induced
cravings.
SUMMARY
[0147] In sum, the various methods used in the animal studies
described above show a distinct pattern of brain activation that
results from the selective action of cocaine on particular cortical
and subcortical targets, resulting in neural activation within
specific structures of the brain. The pattern of brain activation
observed with animals shows significant overlap with the pattern of
brain activation observed in humans after acute cocaine
administration. Pretreatment of animals with the D1 receptor
antagonist SCH-23390 attenuated cocaine-induced brain activation,
indicating that the D1 receptor mediates the acute action of
cocaine in the brain, and supporting the conclusion that D1-like
agonists and D1-like antagonists can be used to attenuate
psychostimulant-induced and nicotine-induced cravings in
humans.
Example III
Animal Model System
[0148] Now that the pattern of psychostimulant-induced brain
activation in rodents has been shown to overlap the pattern of
psychostimulant-induced brain activation in humans, rodents can be
used as a model system to measure the ability of test compounds to
inhibit psychostimulant-induced or nicotine-induced craving in
humans. In this method, a test compound of interest is administered
to a rodent prior to administration of a psychostimulant or of
nicotine, and the ability of the test compound to attenuate brain
activation by the psychostimulant or nicotine is measured.
Attenuation of brain activation can be measured by measuring an
attenuation in the level of activation obtained after
administration of (a) the test compound and (b) the psychostimulant
or nicotine, as compared with the level of brain activation
obtained upon (a) administration of the psychostimulant or nicotine
to the rodent without (b) administration of the test compound. Test
compounds that cause such a relative attenuation in the level of
brain activation can be used to inhibit psychostimulant-induced or
nicotine-induced craving in humans.
[0149] In this method, rodents such as rats and mice are suitable.
The rodent can be naive, in that it has not previously been exposed
to pyschostimulants or nicotine, or an animal that was chronically
using a psychostimulant or nicotine may be used. The test compound
generally is administered at a dosage of 0.001 to 100 mg/kg (e.g.,
0.1 to 1.0 mg/kg) of body weight of the rodent. The test compound
can be formulated for administration, and administered, via any of
various routes, such as intravenous, oral, intranasal,
intrabronchial, and intramuscular routes, as described above for
D1-like antagonists and agonists. Typically, the test compound is a
D1-like agonist or antagonist, such as those described herein. The
test compound can be administered to the rodent at 0 minutes to 2
days (e.g., 15 minutes to 1, 2, 4, or 8 hours) prior to
administration of the psychostimulant or nicotine to the mammal.
The psychostimulant (e.g., cocaine or amphetamine) or nicotine
typically is administered at a dosage of 0.1 mg/kg to 10 mg/kg of
body weight of the animal. Attenuation of pyschostimulant-induced
or nicotine-induce brain activation (i.e., a relative decrease in
the level of brain activation) can be measured using any of the
art-accepted methods for measuring levels of brain activation. The
above-described methods of BOLD fMRI, contrast fMRI, and laser
Doppler-flowmetry can be used to measure the ability of a test
compound to attenuate psychostimulant-induced or nicotine-induced
brain activation and thereby inhibit psychostimulant-induced or
nicotine-induced craving. Test compounds that inhibit
psychostimulant-induce or nicotine-induced brain activations in
this animal model can be administered to humans in a method of
inhibiting craving of psychostimulants or nicotine. Typically, the
test compound is administered to the human at a dosage of 0.001 to
100 mg/kg (e.g., 0.1 to 1.0 mg/kg) of body weight of the patient.
The test compounds that inhibit psychostimulant-induce or
nicotine-induced brain activations in rodents can be formulated for
administration, and administered, to humans via any of the various
routes described herein for D1-like agonists and antagonists.
Other Embodiments
[0150] It is to be understood that, while the invention has been
described in conjunction with the detailed description thereof, the
foregoing description is intended to illustrate and not limit the
scope of the invention, which is defined by the scope of the
appended claims. Other aspects, advantages, and modifications are
within the scope of the following claims.
* * * * *