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Volume 16, Number 10,
Issue of May 15, 1996
pp. 3507-3510
Copyright ©1996 Society for Neuroscience
The Vesicular Monoamine Transporter, in Contrast to the Dopamine
Transporter, Is Not Altered by Chronic Cocaine Self-Administration
in the Rat
Julie M. Wilson and
Stephen J. Kish
Human Neurochemical Pathology Laboratory, Clarke Institute of
Psychiatry, Toronto, Ontario, Canada M5T 1R8
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
FOOTNOTES
REFERENCES
ABSTRACT
Although much evidence suggests that the brain dopamine transporter
(DAT) is susceptible to dopaminergic regulation, only limited
information is available for the vesicular monoamine transporter
(VMAT2). In the present investigation, we used a chronic,
unlimited-access, cocaine self-administration paradigm to determine
whether brain levels of VMAT2, as estimated using
[3H]dihydrotetrabenazine (DTBZ) binding, are
altered by chronic exposure to a dopamine uptake blocker. Previously,
we showed that striatal and nucleus accumbens DAT levels, as estimated
by [3H]WIN 35,428 and
[3H]GBR 12,935 binding, are altered markedly
using this animal model (Wilson et al., 1994 ). However, in sequential
sections from the same animals, [3H]DTBZ
binding was normal throughout the entire rostrocaudal extent of the
basal ganglia (including striatum and nucleus accumbens), cerebral
cortex, and diencephalon, as well as in midbrain and brainstem
monoamine cell body regions, both on the last day of cocaine access and
after 3 weeks of drug withdrawal. These data provide additional
evidence that VMAT2, unlike DAT, is resistant to dopaminergic
regulation.
Key words:
cocaine;
vesicular monoamine transporter;
dihydrotetrabenazine;
quantitative autoradiography;
self-administration;
unlimited access
INTRODUCTION
In dopaminergic nerve terminals, dopamine is
packaged into synaptic vesicles by the vesicular monoamine transporter
(VMAT2). Synaptic vesicles exist in two functional pools: a releasable
pool and a reserve pool (Greengard et al., 1993 ; Kelly, 1993 ). Vesicles
in the releasable pool are held close to the plasma membrane, and upon
depolarization of the nerve terminal, release dopamine into the
synaptic cleft where it can interact with receptors to initiate a
cellular response. The vesicles in the reserve pool, in contrast, are
linked to the cytoskeleton and are recruited to the release pool to
maintain the physiological requirements of the cell. Neurotransmission
is terminated by the removal of dopamine from its site of action,
mediated primarily through reuptake into the presynaptic nerve terminal
via the plasma membrane dopamine transporter (DAT). Once inside the
nerve terminal, dopamine can be stored in a cytoplasmic pool or
packaged into synaptic vesicles via VMAT2. Both DAT and VMAT2 have been
proposed as indices of presynaptic nerve terminal integrity.
Radiotracers have been developed for imaging these sites using
in vitro (ligand binding and autoradiography) and
in vivo (positron emission tomography and single photon
emission computerized tomography techniques) (Schoemaker et al., 1985 ;
Scherman et al., 1988 ; Frost et al., 1993 ; Innes, 1994 ; Vander Borght
et al., 1995 ).
Experimental evidence suggests that striatal and nucleus accumbens DAT
levels, as estimated by radioligand binding techniques, can be altered
markedly, independent of changes in dopamine nerve terminal density, to
maintain normal synaptic dopamine levels. Although the data are not
entirely consistent (see Wilson et al., 1994 ), striatal DAT
concentrations can be elevated after administration of drugs that
enhance synaptic dopamine levels (Weiner et al., 1989 ; Vander Borght et
al., 1995 ) and reduced after administration of dopamine-depleting drugs
(Kilbourn et al., 1992 ). Similarly, during chronic administration of
the dopamine uptake blocker cocaine, which results in elevated synaptic
dopamine levels (Pettit and Justice, 1991 ), DAT levels are increased
(Alburges et al., 1993 ; Wilson et al., 1994 ), whereas during cocaine
withdrawal, a state associated with subnormal synaptic dopamine
concentrations (Parsons et al., 1991 ), DAT levels are reduced (Hitri et
al., 1989 ; Sharpe et al., 1991 ; Farfel et al., 1992 ; Wilson et al.,
1994 ). Although these data suggest that DAT is subject to dopaminergic
regulation, the mechanism through which the regulatory changes are
mediated remains to be determined. However, some evidence suggests the
involvement of the dopamine D2 receptor in modulating DAT function
(Cass and Gerhardt, 1994 ).
Only limited information is available with respect to the
susceptibility of VMAT2 to dopaminergic regulation. Although two recent
investigations have suggested that VMAT2 is not regulated readily by
drugs that alter synaptic dopamine concentration or dopamine receptor
function (Naudon et al., 1994 ; Vander Borght et al., 1995 ), these
studies have been limited to short-term drug treatments (2 d and 2 weeks, respectively). Therefore, in the present investigation, we
assessed whether binding of
[3H]dihydrotetrabenazine (DTBZ) to VMAT2 is
altered after chronic (7 weeks) perturbation of the dopamine system
with cocaine. An unlimited-access self-administration paradigm was
used, in which rats received high doses of cocaine (~90 mg/kg per
day). This paradigm has previously demonstrated marked up- and
downregulation of the DAT during cocaine access and withdrawal,
respectively (Wilson et al., 1994 ).
MATERIALS AND METHODS
An unlimited cocaine self-administration paradigm was used to
investigate the influence of prolonged, high-dose cocaine exposure on
VMAT2. The results presented here were obtained from sequential brain
sections from the same animals used in a previous investigation, in
which [3H]WIN 35,428 and
[3H]GBR 12,935 binding to the DAT was measured,
and in which the self-administration paradigm has been described in
detail (Wilson et al., 1994 ). Briefly, male Wistar rats (350 to 400 gm)
were implanted with chronic indwelling jugular vein catheters and
allowed to recover from surgery for 24-48 hr. The rats lived in their
operant chambers for the duration of the experiment. The chambers
contained two response levers, a food receptacle, and a standard water
bottle. A stimulus light was mounted above each lever and was
illuminated for the duration of an infusion (3-4 sec) after a response
was made. Infusion pumps were located outside sound-attenuating wooden
enclosures. One to 2 d after surgery, the drug-naive rats, with no
previous experience in the operant chamber, were given unlimited access
to cocaine self-administration. Daily sessions began at 10:00 A.M. and
lasted 24 hr/d for at least 3 weeks (mean self-administration period = 7 weeks ± 5 d). Cocaine (0.1 mg per infusion) was delivered after a
response on the left lever, and the dose was controlled by the duration
of infusion (1 sec per 100 gm body weight). Food intake was limited to
20 gm/d during the self-administration period. Because the experimental
chamber acts as the home environment for the
self-administering animals, control animals (n = 15, age-
and food-matched) remained in their home cages throughout.
One group of rats (on-cocaine group, n = 10) was killed on
the last day of cocaine access with no withdrawal from cocaine. The
maximal interval between the last cocaine infusion and death was 4 hr.
A second group (cocaine-withdrawn group, n = 8) was killed
after a 3 week withdrawal period. Rats were killed by decapitation and
the brain removed rapidly and divided longitudinally into two halves.
One half was frozen immediately over dry ice and stored at 80°C
until cryostat sectioning. Serial coronal sections (20 µm) were cut
at 20°C, thaw mounted onto gelatin-coated slides, and stored at
80°C until assayed. The second half was dissected over a cold plate
into discrete brain areas that were stored at 80°C and retained for
measurement of monoamines and metabolites (Wilson et al., 1994 ).
Binding of [3H]DTBZ to the vesicular monoamine
transporter was assessed using minor modifications of the procedure of
Rostène and colleagues (1992). Brain sections were preincubated
for 20 min at 25°C in 50 mM sodium phosphate
buffer, pH 7.7, to remove any residual cocaine that might be present,
then incubated for 40 min in the same buffer containing 5 nM [3H]DTBZ (155 Ci/mmol,
Amersham, Oakville, Ontario, Canada) in the presence (nonspecific
binding) or absence (total binding) of 2 µM
tetrabenazine. The concentration of [3H]DTBZ
was equal to the equilibrium dissociation constant
(Kd) for [3H]DTBZ
binding in rat striatum (Darchen et al., 1989 ) and was chosen to permit
detection of changes in both affinity (Kd)
and density (Bmax) of VMAT2. Sections were
washed twice in buffer at 0-4°C for 3 min and rinsed in distilled
water before drying. Dried sections were apposed to tritium-sensitive
film (Eastman Kodak Hyperfilm, Rochester, NY) at 0-4°C for 2 weeks
in the presence of tritium-calibrated 14C-labeled
standards. Films were developed using Kodak D19 developer, and
densitrometric analysis of autoradiograms was performed using a
camera-based computerized imaging device (MCID, Imaging Research, St.
Catharines, Ontario, Canada).
As described in detail previously (Wilson et al., 1994 ), brain areas
were subdivided in anterior-posterior, dorsoventral, and mediolateral
planes where appropriate.
RESULTS
Cocaine self-administration
The mean daily cocaine intake in rats given unlimited access to
self-administration of cocaine was 36.8 ± 4.2 mg/d (~90 mg/kg per
day). There were no statistically significant differences (using an
unpaired Student's t test) in mean daily cocaine intake
between the on-cocaine (42 ± 4 mg) and cocaine-withdrawn (30 ± 8 mg)
groups. In addition, there were no significant differences between
total cocaine intake (on-cocaine, 1700 ± 290 mg; cocaine-withdrawn,
1690 ± 350 mg; p > 0.05), maximum daily intake
(on-cocaine, 132 ± 18 mg; cocaine-withdrawn, 111 ± 26 mg;
p > 0.05), or duration of access (on cocaine, 41 ± 6 d;
cocaine-withdrawn, 60 ± 7 d; p > 0.05) between the
on-cocaine and cocaine-withdrawn groups. The daily patterns of cocaine
intake have been described previously (Wilson et al., 1994 ).
Vesicular monoamine transporter distribution in control brain
Specific [3H]DTBZ binding was detected in
dopamine (striatum, nucleus accumbens, olfactory tubercle, substantia
nigra, ventral tegmental area), noradrenaline (hypothalamus, septum,
locus coeruleus), and serotonin (dorsal raphe) brain areas (Table
1). The highest density of
[3H]DTBZ binding was in the basal ganglia
(striatum, nucleus accumbens) and olfactory tubercle. Subregional
analysis of the binding data revealed a heterogeneous pattern of
binding in dopaminergic nerve terminal areas, with rostrocaudal and
mediolateral gradients being evident in striatum. Thus,
[3H]DTBZ binding was more dense in the anterior
than posterior regions of the striatum (rostral pole, 257 pmol/µg
tissue; caudal body, 180 pmol/µg tissue) and nucleus accumbens
(anterior, 254 pmol/µg tissue; posterior, 223 pmol/µg tissue). The
rostral pole and rostral body of the striatum displayed a slight
decreasing mediolateral gradient, although this was reversed in
intermediate striatum, with the lateral portion displaying the highest
density of binding. Dorsoventral gradients were evident only in the
caudal body of the striatum in which the ventral subdivision showed the
highest binding (ventral, 248 pmol/µg tissue; dorsal 128 pmol/µg
tissue).
Table 1.
[3H]DTBZ binding in rat brain: influence of
chronic unlimited access to self-administration of
cocaine
| Brain
region |
Control |
On-cocaine |
Withdrawn |
|
| Cortex |
| Frontal |
12.7
± 0.2 |
9.0 ± 0.7 |
8.1 ± 1.1 |
| Cingulate |
12.2
± 0.7 |
13.5 ± 1.1 |
12.5 ± 1.3 |
| Limbic |
20.4
± 0.9 |
21.7 ± 1.6 |
18.7 ± 2.0 |
| Occipital |
5.2
± 0.2 |
5.3 ± 0.8 |
3.9 ± 0.8 |
| Basal ganglia |
| Nucleus
accumbens |
| Whole |
240 ± 5 |
231 ± 10 |
224
± 10 |
| Anterior |
254 ± 6 |
234 ± 8 |
233
± 12 |
| Posterior |
224 ± 3 |
226 ± 14 |
218
± 9 |
| Striatum |
| Whole |
202 ± 2 |
198 ± 9 |
191
± 10 |
| Rostral pole |
257 ± 10 |
227 ± 16 |
229
± 12 |
| Dorsomedial |
266 ± 15 |
228 ± 26 |
235
± 19 |
| Dorsolateral |
248 ± 9 |
213 ± 14 |
235
± 14 |
| Ventromedial |
273 ± 10 |
260
± 11 |
241 ± 16 |
| Ventrolateral |
225 ± 11 |
206
± 13 |
201 ± 12 |
| Rostral body |
238 ± 5 |
233
± 14 |
231 ± 10 |
| Dorsomedial |
248 ± 9 |
250
± 18 |
249 ± 10 |
| Dorsointermed. |
232 ± 6 |
241
± 15 |
227 ± 11 |
| Dorsolateral |
229 ± 8 |
223
± 11 |
220 ± 8 |
| Intermed.-medial |
265 ± 8 |
254
± 16 |
262 ± 12 |
| Intermed.-intermed. |
215
± 6 |
210 ± 12 |
203 ± 11 |
| Intermed.-lateral |
209
± 7 |
203 ± 10 |
198 ± 12 |
| Ventromedial |
266
± 7 |
251 ± 16 |
258 ± 12 |
| Ventrointermed. |
245
± 6 |
239 ± 16 |
236 ± 11 |
| Ventrolateral |
238
± 5 |
228 ± 15 |
226 ± 13 |
| Intermediate body |
199
± 4 |
209 ± 12 |
194 ± 12 |
| Dorsomedial |
202
± 8 |
230 ± 16 |
211 ± 14 |
| Dorsointermed. |
188
± 6 |
199 ± 15 |
182 ± 13 |
| Dorsolateral |
212
± 9 |
212 ± 9 |
194 ± 15 |
| Intermed.-medial |
174
± 6 |
186 ± 16 |
175
± 14 |
| Intermed.-intermed. |
169 ± 3 |
173
± 11 |
158 ± 10 |
| Intermed.-lateral |
212 ± 7 |
212
± 6 |
187 ± 10 |
| Ventromedial |
169 ± 7 |
164
± 11 |
163 ± 10 |
| Ventrointermed. |
218 ± 6 |
221
± 10 |
209 ± 11 |
| Ventrolateral |
256 ± 7 |
257
± 9 |
233 ± 15 |
| Caudal body |
179 ± 3 |
174
± 6 |
168 ± 10 |
| Dorsal |
129 ± 5 |
132
± 7 |
130 ± 10 |
| Intermed. |
170 ± 4 |
162
± 6 |
156 ± 11 |
| Ventral |
248 ± 7 |
235
± 9 |
227 ± 13 |
| Caudate tail |
112 ± 5 |
109
± 8 |
97 ± 7 |
| Bed nucleus of stria
terminalis |
| Anterior |
89 ± 5 |
80 ± 6 |
93
± 7 |
| Ventral |
148 ± 9 |
145 ± 10 |
130
± 11 |
| Fundus striati |
221 ± 6 |
187 ± 24 |
195
± 19 |
| Globus pallidus |
11.7 ± 0.8 |
11.8
± 1.0 |
9.8 ± 1.6 |
| Basal forebrain |
| Olfactory
tubercle |
| Whole |
192 ± 5 |
182 ± 5 |
185
± 5 |
| Anterior |
192 ± 6 |
183 ± 4 |
185
± 6 |
| Posterior |
188 ± 7 |
181 ± 8 |
182
± 4 |
| Lateral septum |
| Dorsal |
208 ± 7 |
256
± 19 |
239 ± 9 |
| Intermed. |
58 ± 3 |
78
± 10 |
69 ± 6 |
| Ventral |
172 ± 6 |
196
± 19 |
191 ± 13 |
| Medial septum |
47 ± 5 |
49
± 6 |
45 ± 8 |
| Pyramidal cell layer |
22 ± 1 |
25
± 2 |
22 ± 3 |
| Hippocampus |
12 ± 1 |
14
± 1 |
12 ± 1 |
| Basolateral amygdala |
51 ± 2 |
54
± 3 |
48 ± 3 |
| Diencephalon |
| Suprachiasmatic
nucleus |
89 ± 14 |
80 ± 9 |
57 ± 14 |
| Supraoptic
nucleus |
145 ± 9 |
151 ± 10 |
167
± 11 |
| Paraventricular nucleus |
150 ± 8 |
183
± 14 |
160 ± 13 |
| Hypothalamus |
| Anterior |
61
± 3 |
76 ± 4 |
62 ± 4 |
| Dorsomedial |
79
± 7 |
83 ± 5 |
79 ± 8 |
| Ventromedial |
57
± 3 |
56 ± 4 |
58 ± 3 |
| Lateral preoptic area |
51
± 3 |
54 ± 6 |
53 ± 5 |
| Medial preoptic area |
80
± 3 |
88 ± 3 |
77 ± 6 |
| Habenula |
| Medial |
28
± 2 |
31 ± 4 |
30 ± 3 |
| Lateral |
16 ± 5 |
11
± 2 |
15 ± 4 |
| Thalamus |
| Anteroventral thalamic
nucleus |
55 ± 3 |
51 ± 3 |
54 ± 5 |
| Paratenial
thalamic nucleus |
74 ± 9 |
72 ± 11 |
75
± 7 |
| Paraventricular thalamic nucleus |
88 ± 6 |
87
± 7 |
100 ± 12 |
| Midbrain |
| Substantia nigra |
92
± 8 |
82 ± 5 |
81 ± 7 |
| Ventral tegmental area |
101
± 5 |
94 ± 6 |
91 ± 8 |
| Superior colliculus |
27
± 1 |
29 ± 2 |
25 ± 2 |
| Periaqueductal grey |
33
± 2 |
37 ± 3 |
34 ± 4 |
| Medial raphe |
56
± 14 |
43 ± 12 |
61 ± 13 |
| Dorsal raphe |
144
± 12 |
148 ± 11 |
140 ± 21 |
| Subincertal nucleus |
55
± 3 |
51 ± 4 |
44 ± 3 |
| Brainstem |
| Locus
coeruleus |
174 ± 39 |
267 ± 23 |
209 ± 47 |
|
|
Data are subregional distribution (mean ± SEM; pmol/µg
tissue) of [3H]DTBZ binding in brain of control rats
(n = 15) and of rats killed on the last day of (n = 10) or 3 weeks after withdrawal from (n = 8) chronic,
unlimited access to self-administration of cocaine.
|
|
Vesicular monoamine transporter distribution in cocaine
exposed brain
No significant changes in [3H]DTBZ binding
to the VMAT2 were detected in any brain area after chronic cocaine
self-administration, either on the last day of cocaine access or after
3 weeks of drug withdrawal (Table 1). In contrast, levels of DAT (as
assessed using [3H]WIN 35,428 and
[3H]GBR 12,935 binding) in striatum and nucleus
accumbens were up- and downregulated during cocaine access and
withdrawal, respectively (Fig. 1) (see Wilson et al.,
1994 ).
Fig. 1.
Bars represent [3H]WIN 35,428, [3H]GBR 12,935, and [3H]DTBZ binding
(expressed as a percentage of control, n = 15) in striatum
and nucleus accumbens (nacs) of rats exposed to unlimited-access
cocaine self-administration and killed on the last day of cocaine
access (n = 10) (hatched bars) or 3 weeks
after drug withdrawal (n = 8) (black bars).
One-way ANOVA, followed by Fisher's least significant difference test
(asterisk indicates p < 0.05; double
asterisk indicates p < 0.001). Data for
[3H]WIN 35,428 and [3H]GBR
12,935 bindings are taken from Wilson et al. (1994) .
[View Larger Version of this Image (34K GIF file)]
DISCUSSION
VMAT2 in normal rat brain
The distribution of [3H]DTBZ binding
correlated with monoaminergic-rich brain areas, as described previously
(Scherman, 1986 ; Scherman et al., 1986 ; Scherman et al., 1988 ; Darchen
et al., 1989 ; Rostene et al., 1992). The highest density of
[3H]DTBZ binding was in the dopamine-rich areas
of striatum, nucleus accumbens, and olfactory tubercle. Lesions of the
nigrostriatal pathway with 6-hydroxydopamine result in a marked
depletion of [3H]DTBZ binding sites in rat
striatum (Darchen et al., 1989 ; Masuo et al., 1990 ), together with
reduced tyrosine hydroxylase activity (Masuo et al., 1990 ), suggesting
that a substantial proportion (~95%) of striatal
[3H]DTBZ binding is to dopaminergic nerve
terminals (Masuo et al., 1990 ). Based on the relative concentrations of
dopamine and serotonin in striatum, it generally is assumed that only
~5% of monoaminergic neurons in the striatum are serotonergic
(Scherman et al., 1986 ).
The subregional distribution of [3H]DTBZ
binding revealed a heterogeneous pattern of binding in dopaminergic
nerve terminal areas. The rostrocaudal gradient observed for
[3H]DTBZ binding in the striatum was similar to
that reported previously for [3H]GBR 12,935 and
[3H]WIN 35,428 binding (Wilson et al., 1994 ),
with the highest density observed in the rostral body. Similarly, a
clear dorsoventral gradient was observed for all three ligands in the
caudal body of the striatum, with the highest binding density detected
in the ventral subdivision. Previously we have reported differential
localization of [3H]GBR 12,935 and
[3H]WIN 35,428 binding sites (highest density
in dorsomedial and ventrolateral subdivisions, respectively) in the
rostral body of the striatum (Wilson et al., 1994 ), suggesting that
these ligands might bind to different affinity states or variants of
the DAT. The density gradients observed for
[3H]DTBZ binding in the striatum could reflect
a composite of [3H]GBR 12,935 and
[3H]WIN 35,428 binding sites, suggesting that
[3H]DTBZ binds to all dopaminergic nerve
terminals, irrespective of the expressed form of DAT.
Although [3H]DTBZ binding is predominantly to
dopaminergic nerve terminals in the basal ganglia, significant binding,
as expected, was detected in other brain areas that contain
noradrenergic and serotonergic innervation (hypothalamus, septum), as
well as in the corresponding cell body areas (locus coeruleus and raphe
nuclei).
Cocaine and the vesicular monoamine transporter
The present results demonstrate that
[3H]DTBZ binding in rat brain was unaltered
after chronic, unlimited access to self-administration of high doses
(~90 mg/kg per day) of cocaine, both on the last day of cocaine
access and after a 3 week withdrawal period. These findings are
consistent with the recent demonstration from two independent studies
(Naudon et al., 1994 ; Vander Borght et al., 1995 ) that pharmacological
agents that modify synaptic dopamine concentration (mazindol, deprenyl,
L-dopa) or dopamine receptor function (haloperidol,
bromocriptine, apomorphine) do not alter brain VMAT2 concentration.
This is in contrast to DAT, which undergoes marked up- and
downregulation after administration of drugs that enhance (Weiner et
al., 1989 ; Vander Borght et al., 1995 ) and reduce (Kilbourn et al.,
1992 ), respectively, synaptic dopamine concentrations. Thus, whereas
DAT regulation might reflect a compensatory change to modify synaptic
dopamine concentrations and to maintain dopaminergic neurotransmission
at more normal levels, VMAT2 appears to be highly resistant to such
compensatory changes. However, although these data suggest that there
is no change in the total number of synaptic monoamine-containing
vesicles, it is unknown whether the proportion of releasable versus
reserve pools of vesicles (for review, see Greengard et al., 1993 ) are
altered. In this regard, it is conceivable that the efficiency of
dopaminergic neurotransmission could be modulated by a shift in the
relative number of synaptic vesicles available at the plasma membrane
for exocytosis, without the need for alterations in vesicle synthesis
or degradation (cf. Greengard et al., 1993 ).
In conclusion, the present data provide additional support to the
suggestion that total VMAT2 levels are not readily susceptible to
dopaminergic regulation. Consequently, measurement of the
[3H]DTBZ binding site on VMAT2 might provide an
objective estimate of monoaminergic nerve terminal integrity (Vander
Borght et al., 1995 ). In this regard, the present data are consistent
with those from other investigations (Ryan et al., 1988 ; Seiden and
Kleven, 1988 ; Bennet et al., 1993a,b), which suggest that chronic
cocaine exposure is not associated with actual loss of dopaminergic
nerve terminals in rat brain.
FOOTNOTES
Received Jan. 23, 1996; revised Feb. 29, 1996; accepted March 4, 1996.
This study was supported by National Institutes of Health NIDA DA07182
(S.J.K.). J.M.W. is the recipient of a Commonwealth Scholarship
Award.
Correspondence should be addressed to Dr. Stephen J. Kish, Human
Neurochemical Pathology Laboratory, Clarke Institute of Psychiatry, 250 College Street, Toronto, Ontario, Canada M5T 1R8.
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