Download Contrasting Effects of Haloperidol and Lithium on

PRIORITY COMMUNICATION
Contrasting Effects of Haloperidol and Lithium on
Rodent Brain Structure: A Magnetic Resonance
Imaging Study with Postmortem Confirmation
Anthony C. Vernon, Sridhar Natesan, William R. Crum, Jonathan D. Cooper, Michel Modo,
Steven C.R. Williams, and Shitij Kapur
Background: Magnetic resonance imaging (MRI) studies suggest that antipsychotic -treated patients with schizophrenia show a decrease
in gray-matter volumes, whereas lithium-treated patients with bipolar disorder show marginal increases in gray-matter volumes. Although
these clinical data are confounded by illness, chronicity, and other medications, they do suggest that typical antipsychotic drugs and lithium
have contrasting effects on brain volume.
Methods: Rodent models offer a tractable system to test this hypothesis, and we therefore examined the effect of chronic treatment (8
weeks) and subsequent withdrawal (8 weeks) with clinically relevant dosing of an antipsychotic (haloperidol, HAL) or lithium (Li) on brain
volume using longitudinal in vivo structural MRI and confirmed the findings postmortem using unbiased stereology.
Results: Chronic HAL treatment induced decreases in whole brain volume (⫺4%) and cortical gray matter (⫺6%), accompanied by
hypertrophy of the corpus striatum (⫹14%). In contrast, chronic Li treatment induced increases in whole-brain volume (⫹5%) and cortical
gray matter (⫹3%) without a significant effect on striatal volume. Following 8 weeks of drug withdrawal, HAL-induced changes in brain
volumes normalized, whereas Li-treated animals retained significantly greater total brain volumes, as confirmed postmortem. However, the
distribution of these contrasting changes was topographically distinct: with the haloperidol decreases more prominent rostral, the lithium
increases were more prominent caudal.
Conclusions: The implications of these findings for the clinic, potential mitigation strategies, and further drug development are discussed.
Key Words: Antipsychotic, brain volume, haloperidol, lithium,
magnetic resonance imaging, schizophrenia
he effects of psychotropic medications have predominantly
been presumed to be neurochemical. However, it is increasingly being realized that chronic psychotropic treatment may
lead to structural remodeling of the brain, although it remains to be
determined whether these changes are related to their positive
effects or whether they have any negative implications (1– 4).
However, recent data emerging from clinical studies suggest an
intriguing picture: chronic treatment with antipsychotic drugs is
associated with a decrease in brain cortical volume, whereas treatment with the mood stabilizer lithium (Li) is associated with an
increase in cortical brain volume. Haloperidol (HAL), a prototypical
typical antipsychotic drugs, has been widely cited to induce
changes in brain volume, including enlargement of the caudate
nucleus (1,5– 8) and reductions in cortical gray matter (1,2,6,9 –11).
In contrast, increasing brain gray matter is well documented with Li
treatment (3,4,12–15). Understandably, these data have limitations.
Patients are not assigned to placebo for long periods of time, and
the interpretations are often confounded by illness duration, chronicity, and severity thereafter. Furthermore, patients have concomitant illnesses and medications. Nonetheless, these data support a
T
From the Departments of Psychosis Studies (ACV, SN, SK), Institute of Psychiatry, King’s College London; Department of Neuroimaging (WRC,
SCRW), Centre for Neuroimaging Sciences, Institute of Psychiatry; Department of Neuroscience (JDC, MM), Institute of Psychiatry, The James
Black Centre, King’s College London, London, United Kingdom.
Authors ACV and SN contributed equally to this work.
Address correspondence to Shitij Kapur, M.D., Ph.D., FRCPC, King’s College
London, Institute of Psychiatry, Box P0 01, De Crespigny Park, London,
United Kingdom, SE5 8AF; E-mail: [email protected].
Received Sep 28, 2011; revised Nov 22, 2011; accepted Dec 1, 2011.
0006-3223/$36.00
doi:10.1016/j.biopsych.2011.12.004
testable hypothesis that HAL and Li have contrasting effects on
brain volume. Rodent models offer an effective way to test this
hypothesis, affording precise control over drug exposure, age, concomitant medications, and conditions.
However, preclinical studies often lack clinically comparable
dosing regimens, and longitudinal noninvasive imaging technology has rarely been used. The two most common approaches to
bridge clinical and preclinical studies are to match brain receptor
occupancy or therapeutically acceptable drug plasma levels
(16,17). Because human dosing intervals are of the order of one
pharmacokinetic half-life, animals would have to be injected several times a day to maintain a comparable human plasma concentration for HAL (rodent t1/2 1.5 hour vs. human t1/2 12–36 hours) and
Li (rodent t1/2 3.5 hours versus human t1/2 20 –24 hours) (16,18). We
have developed a rat model using clinically relevant drug exposure
through use of continuous infusion pumps that provide constant
drug delivery and matched clinical dosing in combination with
longitudinal magnetic resonance imaging (MRI) (19). In the current
study, we have used this powerful systems-level approach to address four new questions: 1) Does chronic treatment with HAL and
Li result in contrasting effects on brain volume? 2) Are drug effects
on brain volume global or limited to specific regions? 3) Are drug
effects on brain volume reversible after drug withdrawal? 4) Are
changes seen on the MRI verifiable postmortem?
Methods and Materials
Animals
Male Sprague-Dawley rats (Charles River UK, Kent, United Kingdom), initial body weight 240 to 250 g (9 weeks of age) were housed
4 per cage under a 12-hour light– dark cycle (7 AM lights on) with
food and water available ad libitum. Room temperature was maintained at 21° ⫾ 2°C and relative humidity at 55% ⫾ 10%. Animals
were habituated for 7 days before experimental procedures. Animal experiments were carried out with local ethical approval and in
BIOL PSYCHIATRY 2012;xx:xxx
© 2012 Society of Biological Psychiatry
2 BIOL PSYCHIATRY 2012;xx:xxx
accordance with the Home Office Animals (Scientific Procedures)
Act, United Kingdom.
Experimental Design
The experimental design was as described previously (19), and
none of experiments in the present study overlapped with the
previous one. Briefly, animals were randomly assigned to one of
four treatment groups: 1) vehicle (␤-hydroxypropylcyclodextrin,
20% w/v, acidified by ascorbic acid, to pH 6); 2) .5 mg/kg/day HAL
(low-HAL); 3) 2 mg/kg/day HAL (high-HAL); (Sigma-Aldrich, Dorset,
United Kingdom); or 4) 2 mmol/L equiv/kg/day lithium chloride
(Sigma-Aldrich). Each treatment group initially comprised 10 animals. Vehicle or drugs were administered subcutaneously from the
10th week of life, using MRI-safe osmotic minipumps (Alzet Model
2ML4, 28 days; Alzet, Cupertino, California) for 8 weeks, equivalent
to approximately 5 human years assuming 11.8 rat days equals 1
human year (20). During drug treatment, Li-treated animals were
given access to .9% saline instead of tap water to minimize diuretic
properties of Li (17), and this was provided to all animals in all
treatment groups. Subsequently, animals underwent drug withdrawal for 8 weeks. The doses of HAL were chosen on the basis of
65% to 90% striatal D2 receptor occupancy (16,21), whereas the Li
dose was chosen on the basis of previous rodent in vivo data reporting serum plasma levels within the clinical therapeutic range (.4 –
1.2 mmol/mL/L) (17,22–24).
Minipumps filled with drug or vehicle solutions were inserted
subcutaneously on the back flank under isoflurane anaesthesia (5%
induction, 1.5% maintenance) and replaced once after 28 days. In
vivo MRI scans were acquired at baseline before surgery, 8 weeks
after the start of drug treatment and another 8 weeks after the end
of drug treatment. Animals were then sacrificed by cardiac perfusion (.9% saline followed by 4% paraformaldehyde) under terminal
anaesthesia (sodium pentobarbital, 60 mg/kg intraperitoneal).
Postmortem brain volumes were measured using the Cavalieri estimator probe from Nissl-stained serial coronal sections (40 ␮m,
interval 1/12) as previously described (19). Dyskinetic behavior, that
is, vacuous chewing movements (VCM) and body weight were assessed at baseline then biweekly until termination as previously
described (19). A blood sample was collected after 8 weeks of drug
treatment for commercial estimation of plasma drug levels.
MRI Acquisition and Analysis
In vivo T2-weighted magnetic resonance (MR) images were acquired from each animal in a random order interspersed with phantoms to ensure consistent operation. Images were acquired using a
7.0-T horizontal small bore magnet (Varian, Palo Alto, California), as
previously described (19,25) (see also Supplement 1). Before analysis, MR images were visually inspected for motion, intensity, or
gross anatomical malformation, and scans displaying such artifacts
were excluded from further analysis. One animal from the vehicle
group did not survive the 8-week MRI scan because of respiratory
failure. Therefore, final MRI scans analyzed per group at each time
point were vehicle, n ⫽ 9; low-HAL, n ⫽ 7; high-HAL, n ⫽ 8; Li, n ⫽ 9.
Whole-brain volume, total intracranial volume, cerebral cortex, and
subcortical structures (lateral ventricles, hippocampal formation,
and corpus striatum) volumes were delineated manually from in
vivo MR images by two raters (ACV and SN) blinded to treatment
group, using the region-of-interest tool in JIM software (v5.0; Xinapse Systems, Northants, United Kingdom) (19,25). Anatomic
landmarks and reference to the rodent brain atlas (26) were used to
define region-of-interest contours (Table S1 in Supplement 1) exemplified in Figure S1 of Supplement 1. Volumes were calculated by
multiplying the sum of the areas of a given structure on all slices
www.sobp.org/journal
A.C. Vernon et al.
measured by the slice thickness (.6 mm). Intrarater and interrater
reliability were assessed following repeated measurements using
the intraclass correlation coefficient (27). Total cortex (CTX) volume
for each individual slice from each animal acquired after 8 weeks of
drug or vehicle treatment were also divided into rostral (slices 1– 6,
equivalent to approximately ⫹3.00 to ⫺.12 mm from bregma),
midlevel (slices 7–13; ⫺.72 to ⫺3.36 mm from bregma), or caudal
(slices 14 –21; ⫺3.96 to ⫺7.56 mm from bregma) regions.
Postmortem Tissue Handling and Regional Volume
Measurements
After termination, brains were removed and cryoprotected in
buffered 30% sucrose for 48 hours before storage in tissue cryoprotection solution (25% glycerin [v/v] 30% ethylene glycol [v/v] in .2
mol phosphate buffer). Measurements of brain weight and volume
were repeated at each step in the tissue processing, as described
elsewhere (19). Serial coronal sections (40 ␮m, interval 1/12) were
prepared and Nissl stained using cresyl fast violet solution (10%
w/v, 30 min, room temperature) as previously described (19). A
single observer (ACV), blinded to experimental groups, measured
the volume of the cerebral cortex and corpus striatum using the
Cavalieri estimator probe as previously described (19,28). Gunderson coefficients of error (m1) were calculated and were always less
than .05 (29,30).
Data and Statistical Analysis
Statistics were performed using SPSS 19.0 software (SPSS, Chicago, Illinois). Longitudinal assessment of variables was performed
using two-way repeated-measures analysis of variance with one
between-subject factor (treatment) and one within-subject factor
(time) followed by post hoc Bonferroni test for multiple comparisons. Data for baseline versus Week 8 and baseline versus Week 16
were analyzed separately. Postmortem brain weight/volume and
Cavalieri probe estimates of brain volume were analyzed using
one-way analysis of variance followed by post hoc Bonferroni test
for multiple comparisons. VCMs due to drug treatment were analyzed using the repeated-measures nonparametric Friedman test
followed by pairwise nonparametric comparisons using a Wilcoxon
t test. An ␣ level of .05 was selected.
Results
Plasma Levels and Behavior
Administration of psychotropic drugs by osmotic pump
achieved clinically relevant plasma levels (mean ⫾ SD) of 4.7 ⫾ .32
ng/mL (low HAL), 23.3 ⫾ 1.5 ng/mL (high HAL) and .49 ⫾ .04
mmol/L (Li). All animals increased in body weight over time irrespective of treatment group (Figure 1A; Table 1). HAL-treated animals gained less weight compared with controls, but this did not
reach statistical significance. Chronic Li-treated animals displayed
polyuria, but body weight was comparable to vehicle controls. No
other adverse effects were observed, and animals appeared healthy
throughout the treatment duration.
Stereotypical VCM behavior developed only in HAL-treated animals 2 weeks after initiation of drug treatment, irrespective of dose,
increasing to a maximum by 8 weeks of drug treatment (Figure 1B).
Upon withdrawal of HAL, VCM behavior decreased differentially in a
dose-dependent manner, returning to levels comparable to vehicle-treated animal levels, faster in low-HAL-treated animals than
high-HAL-treated animals.
Dose-Dependent Effects of Chronic Haloperidol Treatment on
Whole-Brain and Regional Brain Volumes
To establish the global effects of HAL, whole-brain (WBV) and
total intracranial volumes (TIV) were measured from in vivo T2-
BIOL PSYCHIATRY 2012;xx:xxx 3
A.C. Vernon et al.
icantly increased with time (Table 2; Figure S3 in Supplement 1), it
did so comparably across treatment groups, hence there was no
effect of HAL on growth per se. Across all treatment groups, WBV
significantly increased with time, and significant main effects of
drug treatment and a time ⫻ treatment interaction were detected
(Table 2; Figure 2A). HAL treatment significantly decreased WBV in a
dose-related manner (low-HAL vs. control ⫺1.9%; p ⬍ .05; high-HAL
vs. control ⫺3.7%; p ⬍ .01; Figure 2A).
To pinpoint areas in the brain that account for smaller WBV
observed after chronic HAL treatment, analysis of regional brain
volumes was conducted. For CTX volume, significant main effects of
drug treatment and a time ⫻ treatment interaction were detected
(Table 2). HAL treatment resulted in a significant decrease in CTX
volume compared with vehicle-treated controls in a dose-related
manner (low-HAL vs. control ⫺1.0%; p ⬍ .05; high-HAL vs. control
⫺5.9%; p ⬍ .01; Figure 2B). Cortical slice profile analysis of Week 8
MR images revealed significant main effects of drug treatment and
slice position, but no slice position ⫻ treatment interaction in rostral, midlevel, and caudal cortical regions (Table 3). Volume decreases in the CTX of HAL-treated animals were confined to the
rostral and midlevel cortex, and more widespread cortical slices
were affected in high- compared with low-HAL-treated animals
(Figure 3A–3F). The volumes of the total corpus striatum (STR; left ⫹
right hemisphere) were significantly increased following chronic
treatment with HAL (Table 2) compared with vehicle-treated animals (low-HAL ⫹8.6%; p ⬍ .05; high-HAL⫹13.6%; p ⬍ .01; Figure
2C). There were no statistically significant effects of chronic HAL
treatment on total lateral ventricle or total hippocampal volume
(Table 2; Figure S3 in Supplement 1).
Figure 1. (A) Changes in body weight during chronic psychotropic drug
treatment and withdrawal. Both low-haloperidol (HAL)-treated (low-HAL;
n ⫽ 10) and high-HAL-treated (n ⫽ 10) animals gained less weight compared
with vehicle-treated controls (n ⫽ 9) after 8 weeks of treatment, although
this did not reach statistical significance. Chronic lithium chloride (LiCl)
treatment had no effect on animal body weight (n ⫽ 10). Data shown are
body weight (mean ⫾ SEM) for each treatment group at each time point. (B)
Chronic HAL but not LiCl treatment induces stereotypical vacuous chewing
movements (VCM) by 2 weeks, maintained until 8 weeks of drug treatment.
Upon withdrawal of HAL, VCM behavior decreased differentially in a dosedependent manner, **p ⬍ .01 low-HAL and high-HAL versus vehicle, respectively. Data shown are mean VCM score ⫾ SEM across time for vehicle and
psychotropic drug treated animals. BL, baseline.
weighted MR images. At baseline, before drug administration,
there were no significant differences in brain volumes across the
treatment groups (Figure S2 in Supplement 1). Although TIV signif-
Effects of Chronic Lithium Treatment on Whole-Brain and
Regional Brain Volumes
We used an identical approach to investigate chronic Li treatment. Although TIV significantly increased with time, it did so comparably across treatment groups, hence there was no effect of Li on
growth per se (Table 2; Figure S3 in Supplement 1). Li treatment
resulted in a significant increase in WBV compared with vehicle
(⫹4.8%; p ⬍ .05; Figure 2A), low-HAL (⫹6.7%; p ⬍ .01), or high-HALtreated animals (⫹8.5%; p ⬍ .01).
Further analysis of regional brain volumes was conducted to
account for increased WBV. Li treatment resulted in a significant
increase in CTX volume when compared with vehicle (⫹3.3%; p ⬍
.01; Table 2; Figure 2B) and either low-HAL (⫹4.0%; p ⬍ .01) or
high-HAL (⫹9.2%; p ⬍ .01) treated animals. Slice profile analysis of
Table 1. Change in Body Weight over Time in Vehicle- and Psychotropic Drug-Treated Animals
Body Weight (g)
Independent
On Drug
Off Drug
Time Point
Vehicle
Low-HALa
High-HALb
Lithiumc
Baseline
Week 2
Week 4
Week 6
Week 8
Week 10
Week 12
Week 14
Week 16
242.7 ⫾ 2.7
308.7 ⫾ 3.0
338.4 ⫾ 4.7
368.0 ⫾ 5.8
392.6 ⫾ 6.6
388.9 ⫾ 7.0
411.7 ⫾ 7.5
425.6 ⫾ 7.3
421.6 ⫾ 7.3
241.6 ⫾ 3.3
298.6 ⫾ 7.6
320.8 ⫾ 9.4
349.5 ⫾ 8.3
362.2 ⫾ 13.4
374.0 ⫾ 13.7
386.6 ⫾ 15.1
402.4 ⫾ 16.5
398.3 ⫾ 16.1
248.3 ⫾ 2.4
289.5 ⫾ 8.8
324.3 ⫾ 4.4
341.6 ⫾ 5.5
363.2 ⫾ 4.7
375.1 ⫾ 7.1
395.4 ⫾ 6.4
407.3 ⫾ 8.2
403.5 ⫾ 8.7
241.3 ⫾ 4.2
306.8 ⫾ 5.2
341.6 ⫾ 6.3
370.0 ⫾ 7.5
389.4 ⫾ 7.9
396.5 ⫾ 7.7
418.2 ⫾ 7.8
430.7 ⫾ 8.7
426.1 ⫾ 8.6
Data shown are body weight (mean ⫾ SEM) for each treatment group across time.
HAL, haloperidol.
a
.5 mg/kg/day subcutaneous.
b
2 mg/kg/day subcutaneous.
c
2 mmol/L equiv/kg/day subcutaneous.
www.sobp.org/journal
4 BIOL PSYCHIATRY 2012;xx:xxx
A.C. Vernon et al.
Table 2. Results of Two-Way Repeated-Measures ANOVA Statistics for Longitudinal In Vivo Magnetic Resonance Imaging Volume Measurements
Effect of Treatment ANOVA
Within Subjects
Between Groups
Time
Time ⫻ Treatment Interaction
F(1,29) ⫽ 4133; p ⬍ .05
F(1,29) ⫽ 2503; p ⬍ .05
F(3,29) ⫽ 3.98; nss
F(3,29) ⫽ 12.69; p ⬍ .05
F(3,29) ⫽ 1.43; nss
F(3,29) ⫽ 6.50; p ⬍ .05
Cerebral Cortex
F(1,29) ⫽ 749.2; p ⬍ .05
F(3,29) ⫽ 9.35; p ⬍ .05
F(3,29) ⫽ 19.32; p ⬍ .05
Corpus Striatum
F(1,29) ⫽ 708.6; p ⬍ .05
F(3,29) ⫽ 6.06; p ⬍ .05
F(3,29) ⫽ 4.23; p ⬍ .05
Hippocampal Formation
Lateral Ventricles
Baseline vs. 16 Weeks
Total Intracranial Volume
Whole Brain Volume
F(1,29) ⫽ 281.8; p ⬍ .05
F(1,29) ⫽ 79.5; p ⬍ .05
F(3,29) ⫽ 1.02; nss
F(3,29) ⫽ 1.46 nss
F(3,29) ⫽ .21; nss
F(3,29) ⫽ .41; nss
F(1,29) ⫽ 2831; p ⬍ .05
F(1,29) ⫽ 3391; p ⬍ .05
F(3,29) ⫽ 1.42; nss
F(3,29) ⫽ 6.97; p ⬍ .05
F(3,29) ⫽ .44; nss
F(3,29) ⫽ 2.64; nss
Cerebral Cortex
Corpus Striatum
Hippocampal Formation
Lateral Ventricles
F(1,29) ⫽ 983.5; p ⬍ .05
F(1,29) ⫽ 600.7; p ⬍ .05
F(1,29) ⫽ 312; p ⬍ .05
F(1,29) ⫽ 179.5; p ⬍ .05
F(3,29) ⫽ 0.42; nss
F(3,29) ⫽ .92; nss
F(3,29) ⫽ .63; nss
F(3,29) ⫽ .54; nss
F(3,29) ⫽ 2.79; nss
F(3,29) ⫽ 1.87; nss
F(3,29) ⫽ 1.48; nss
F(3,29) ⫽ .50; nss
Variable
Baseline vs. 8 Weeks
Total Intracranial Volume
Whole Brain Volume
Treatment
Post Hoc Testa
nd
p ⬍ .05 vehicle vs. low-HAL
p ⬍ .01 vehicle vs. high-HAL
p ⬍ .05 vehicle vs. Li
p ⬍ .05 vehicle vs. low-HAL
p ⬍ .01 vehicle vs. high-HAL
p ⬍ .01 vehicle vs. Li
p ⬍ .01 vehicle vs. low-HAL
p ⬍ .01 vehicle vs. high-HALM
p ⬎ .05 vehicle vs. Li
nd
nd
nd
p ⬎ .05 vehicle vs. low-HAL
p ⬎ .05 vehicle vs. high-HAL
p ⬍ .05 vehicle vs. Li
nd
nd
nd
nd
Drug treatment served as the between-subject factor and time as the within-subject factor. Data shown are comparing baseline to the Week 8 and Week
16 time points.
ANOVA, analysis of variance; HAL, haloperidol; Li, Lithium chloride; nd, no difference; nss, no statistical significance.
a
Bonferroni’s test for multiple comparisons among treatment groups.
Week 8 MR images revealed that CTX volume increases in Li-treated
animals were predominantly in the midlevel and caudal cortical
areas (Table 3; Figure 3G–3I). However, closer examination of the
cortical slice profiles in Li-treated animals suggests a small persisting increase across the whole cortical profile, although not statistically significant (Figure 3G–3I). Li treatment had no significant effect on STR volume compared with vehicle-treated controls (Table
2; Figure 2C). There were no statistically significant effects of
chronic Li treatment on total lateral ventricle and total hippocampal volume (Table 2; Figure S3 in Supplement 1).
Effects of Drug Withdrawal on Whole-Brain and Regional
Brain Volumes
Following drug withdrawal (8 weeks), there were no longer any
significant differences in WBV between vehicle-treated and either
low-HAL- or high-HAL-treated animals (Table 2; Figure 2A). In contrast, to the effects of HAL, WBV remained significantly elevated in
Li-treated animals (Table 2) compared with vehicle (⫹6.3%; p ⬍ .05;
Figure 2A), low-HAL-treated (⫹6.2%; p ⬍ .01) and high-HAL-treated
animals (⫹4.9%; p ⬍ .01).
To determine which brain regions were altered following drug
withdrawal, analysis of regional brain volumes was repeated. After
drug withdrawal, no significant differences in total CTX volume
were observed between vehicle-treated and either low-HAL or
high-HAL-treated animals, or between Li-treated animals and either vehicle, low-, or high-HAL-treated animals (no difference; Table
2; Figure 2B). No significant differences were observed in CTX volume. Slice profile analysis of Week 16 MR images confirmed cortical
volume differences normalized across the three cortical areas following drug withdrawal comparing HAL and vehicle-treated animals (Figure S4 in Supplement 1). Striatal hypertrophy induced by
www.sobp.org/journal
HAL was reversed after drug withdrawal, with no significant differences in total STR volume between low- and high-HAL-treated
animals and vehicle- or Li-treated animals (ns; Table 2; Figure 2C).
Trends toward ventricular hypertrophy were noted in Li-treated
animals, but no statistically significant effects of drug withdrawal
were found for total lateral ventricle and total hippocampal volume
(Figure S3 in Supplement 1).
Postmortem Confirmation of In Vivo MRI
To confirm in vivo MRI measurements made after drug withdrawal, postmortem measurements of brain weight and volume
were obtained and the volume of the CTX and STR assessed histologically using unbiased stereology. The mean fresh weights and
volumes of brains extracted from Li-treated animals were significantly heavier compared with vehicle, low-, or high-HAL-treated
animals (p ⬍ .05; Figure 4A and 4B). Importantly, during the three
phases of tissue processing, brain weight and volume, respectively,
changed in a similar manner across the four exposure groups (Figure S5 in Supplement 1). Histological measurement of the total
volume (left ⫹ right hemisphere) of the CTX and STR using unbiased stereology (Cavalieri estimator probe) revealed no significant
differences in either total CTX volume [F (3,35) ⫽ 2.697; p ⬎ .05;
Figure 4C] or total STR volume [F (3,35) ⫽ .967; p ⬎ .05; Figure 4D]
between treatment groups, thus confirming the in vivo MRI data.
Discussion
This is the first longitudinal in vivo MRI study in rodents to
compare the effects of two commonly prescribed psychotropic
medications on different brain regions. We observed contrasting
effects of treatment (8 weeks) with therapeutically relevant concen-
BIOL PSYCHIATRY 2012;xx:xxx 5
A.C. Vernon et al.
Figure 2. Chronic treatment with
haloperidol (HAL) or lithium chloride (LiCl) results in contrasting effects on whole brain and regional
brain volumes. Chronic HAL treatment (8 weeks) dose-dependently
decreased (A) whole brain volume
and (B) total cortical volume, but
increased striatal volume (C), compared with vehicle-treated animals.
Following drug withdrawal (8
weeks), HAL-induced volumetric
changes were reversed (A–C). In
contrast, chronic LiCl treatment increased (A) whole brain volume
and (B) total cortical volume but
had no effect on striatal volume (C).
Effects of LiCl on whole brain volume were maintained even after
drug withdrawal (A), whereas the
cortical increase normalized (B).
Data shown are mean volume ⫾
SEM; *p ⬍ .05; **p ⬍ .01 HAL versus
vehicle and LiCl versus vehicle, respectively. Total magnetic resonance imaging scans analyzed per
group at each time point: vehicle,
n ⫽ 9; low-HAL, n ⫽ 7; high-HAL,
n ⫽ 8; LiCl, n ⫽ 9 (see Methods and
Materials).
trations of HAL and Li. Specifically, HAL-treatment resulted in doserelated reductions in WBV (up to ⫺3.7%) and CTX (up to ⫺5.9%)
accompanied by hypertrophy of the STR (up to ⫹14%) compared
with vehicle controls. In contrast, Li-treatment resulted in significant increases in WBV (up to ⫹4.8%) and CTX volume (up to ⫹3.3%),
with no effect on the STR, when compared with controls. Following
drug withdrawal (8 weeks, 16 weeks from baseline), the effects of
either dose of HAL on WBV, CTX, and STR volume were reversed. In
contrast, the WBV of Li-treated animals remained elevated, although the effects of Li on CTX volume alone were no longer
significant. These MRI data were confirmed histologically using an
unbiased stereological method, lending certainty to our in vivo
findings.
Comparison of the Effects of Chronic Treatment with HAL or Li
on Brain Morphology
The volume, location and profile of decreases in WBV and CTX in
HAL-treated animals are similar to our previous in vivo study, con-
firming that initial finding (19). These data are consistent with clinical neuroimaging studies of the trajectory of HAL-induced volume
changes in schizophrenia patients (1,2,31). In the current study, as a
result of a larger sample size, we were able to detect striatal hypertrophy due to HAL treatment, which was only observed at trend
level in our previous study (19). These data are consistent with
previous studies in rodents (32,33) and clinical studies (1,2,5–7).
Studies reporting on the loss of gray matter in schizophrenic
patients treated with antipsychotics include a 2.4% decrease in
frontal lobe gray matter volume (2), which is related to dose and
duration of antipsychotic treatment (1). The dosing regimen used in
this study was tailored to capture clinical practice. The lower dose of
HAL chosen for the current study (.5 mg/kg/day) achieves a drug
plasma level within the recommended clinical range of 2 to 5 ng/mL
(16, 34) and results in ⬃1.0% decrease in total cortex volume. The
higher dose of HAL (2 mg/kg/day) achieves plasma levels higher
than the recommended range but still commonly within the range
Table 3. Results of Two-Way ANOVA Statistics for In Vivo Magnetic Resonance Imaging Volume Measurements of
Cortical Slice Profiles (Week 8)
ANOVA
Within Subjects
Variable
Frontal Cortexa
Medial Cortexb
Caudal Cortexc
Between Groups
Slice Position
Slice ⫻ Treatment Interaction
Treatment
F(6,203) ⫽ 96.78; p ⬍ .05
F(6,203) ⫽ 129.5; p ⬍ .05
F(6,203) ⫽ 180.9; p ⬍ .05
F(18,203) ⫽ 1.540; p ⬎ .05
F(18,203) ⫽ .876; p ⬎ .05
F(18,203) ⫽ .936; p ⬎ .05
F(3,203) ⫽ 47.20; p ⬍ .05
F(3,203) ⫽ 65.30; p ⬍ .05
F(3,203) ⫽ 41.67; p ⬍ .05
Drug treatment served as between-subject factor and slice position as within-subject factor.
ANOVA, analysis of variance.
a
Rostral cortex is defined as ⫹3.00 to ⫺.12 mm from bregma.
b
Midlevel cortex is defined as ⫺.72 to ⫺3.36 mm from bregma.
c
Caudal cortex is defined as ⫺3.96 to ⫺7.56 mm from bregma (see Methods and Materials).
www.sobp.org/journal
6 BIOL PSYCHIATRY 2012;xx:xxx
A.C. Vernon et al.
Figure 3. Slice profile analysis of cortical volume changes following 8 weeks of drug or vehicle treatment suggests significant volume decreases in haloperidol
(HAL)-treated animals (A–F) are confined predominantly to rostral and midlevel cortical regions, with more widespread cortical areas affected in high-HAL
(D-F) treated animals than low-HAL (A-C) treated animals, when compared to vehicle-treated controls. In contrast, lithium chloride (LiCl)-treated animals
displayed significant cortical volume increases predominantly in the midlevel and caudal cortical areas (G–I). However, closer examination of the cortical slice
profile in LiCl-treated animals suggests a small, persisting increase across the whole cortical profile, although this does not reach statistical significance at
every slice (G–I). Data shown are mean slice volume at each position ⫾ SEM; *p ⬍ .01 HAL versus vehicle and Li versus vehicle, respectively. Total MRI scans
analyzed per group at each time point: vehicle, n ⫽ 9; low-HAL, n ⫽ 7; high-HAL, n ⫽ 8; LiCl, n ⫽ 9 (see Methods and Materials).
encountered in clinical practice (10 –20 ng/mL) leading to a 6%
decrease in CTX volume. Therefore, the animal data show roughly
comparable findings, which are dose dependent, in the ranges that
are encountered in clinical practice. Yet no effects of HAL treatment
on the volume of the lateral ventricles (LV) or hippocampus were
observed during drug treatment or after withdrawal. LV hypertrophy and decreased hippocampus volume are two of the most replicated imaging findings in schizophrenia (35–37), indicating that
not all anatomic changes are drug-related.
In contrast to HAL, Li-treatment induces an increase in both WBV
and CTX volume, consistent with human studies of Li treatment in
healthy volunteers (38). These data strongly suggest usage of Li
potentially contributes to the heterogeneity in neuroimaging studies of bipolar disorder (39,40). Indeed, Li treatment of patients with
bipolar disorder induces increases in total gray matter (3,4,12,13),
cortical gray matter (12,41), hippocampal (14,15,42) volumes, and
www.sobp.org/journal
LV volumes (40) relative to unmedicated patients and healthy controls after as little as 4 weeks treatment. Our findings in rats are
consistent with these human data, although some notable differences were apparent. In particular, chronic Li treatment did not
significantly alter hippocampal volume in rats. This may be explained by the lack of disease-related neuroanatomic changes in
the young healthy animals used for our model.
Comparison of the Effects of Drug Withdrawal of HAL or Li on
Brain Morphology
Having demonstrated the contrasting effects of HAL and Li on
brain volume, we next investigated how brain volume responds to
withdrawal of drug treatment. Our in vivo MRI data suggest that
HAL-induced morphologic changes are reversible upon drug withdrawal. These data were confirmed histologically and are supported by other studies in animals (32,43,44). Interestingly, a de-
A.C. Vernon et al.
BIOL PSYCHIATRY 2012;xx:xxx 7
Figure 4. Postmortem analysis of brain volume changes
following drug withdrawal. Measurement of (A) fresh
brain weight and (B) volume at dissection confirms a lack
of significant differences between haloperidol (HAL)- and
vehicle-treated animals following 8 wks of drug withdrawal. In contrast, lithium chloride (LiCl)-treated animals
retained significantly enlarged brains compared to vehicle-treated controls, reinforcing the in vivo magnetic resonance imaging findings. Data shown are individual brain
weight (A) or volume (B) (scatter plot with mean), *p ⬍
0.05 Li vs. vehicle; nss, no statistical significance. Reversal
of HAL and lithium chloride (L)-induced changes in cortical (C) and striatal (D) volume was confirmed histologically using the Cavalieri probe method. Data shown are
mean estimated cortical or striatal volume ⫾ SEM. V, vehicle (n ⫽ 9); H(.5), HAL .5 mg/kg/day (n ⫽ 10); H(2), HAL 2
mg/kg/day (n ⫽ 10); L (n ⫽ 10).
crease in caudate nucleus volume was found in a small number of
schizophrenia patients in remission who discontinued atypical antipsychotic medication, whereas caudate nucleus volume increases
were observed in those who continued, consistent with our findings (45). However, gray matter volume continued to decline in the
same patients following discontinuation of antipsychotics (45). This
reinforces the notion that schizophrenia is associated with progressive brain morphologic changes, at least in a subset of patients
(46,47) to which antipsychotic drugs may contribute but are not the
sole cause (1,2). Additional work is required to investigate this phenomenon fully.
To our knowledge, no studies have examined the effect of Li
discontinuation on brain volumes. This is relevant, because the
osmotic effects of Li may lead to neuronal swelling, which might
provide an alternative explanation of increased brain volumes as
opposed to putative neurotrophic/neuroprotective mechanisms
(17,38). The few animal studies on this matter are not consistent,
probably reflecting methodologic differences (48,49). However,
chronic (5-week) Li treatment induced a 3.1% increase in brain
tissue water content in the rostral cortex and hippocampus of rats
(49). In our study, slice profile analyses suggested no significant
increases in the volume of the rostral cortex, nor were there any
significant increases in hippocampal volume following chronic Li
treatment. Furthermore, the observation that WBV remained elevated after drug withdrawal suggests at least a subset of brain
volume changes induced by chronic Li treatment are maintained.
Taken together, these data argue against our data being explained
by purely osmotic effects of Li. However, we cannot ignore the
finding that cortical volume alterations induced by Li were reversed
following drug withdrawal, suggesting that other brain regions are
contributing to the observed WBV increase. Further image analysis
and corroborative histological work is underway to evaluate this.
Neurobiology Underlying Volume Changes due to Chronic
Treatment with Psychotropics
The antipsychotic actions of HAL are attributed to blockade of
D2/3 receptors. However, volume changes observed in our study
include regions that express D2/3 receptors in high-density (striatum) and regions with sparse distribution (prefrontal cortex) (50).
Sustained blockade of D2/3 receptors results in increased dopamine
turnover (51), which may result in oxidative damage through production of cytotoxic free radicals due to auto-oxidation (52). However, the striatum that has the highest concentration of D2/3 receptors, paradoxically, shows hypertrophy in contrast to a volume
decrease in the cortex. Therefore, other mechanisms (Akt and glycogen synthase kinase 3 signaling pathways) (53) or idiosyncratic
mechanisms could be responsible. Of note, primate postmortem
studies suggest chronic antipsychotic drug treatment induces a
reduction in cortical astrocyte number (54,55). These data are consistent with postmortem studies in human schizophrenia brain tissue, suggesting loss of neuropil rather than overt neurodegeneration (56).
In contrast, Li has pleiotropic biological actions, and both human and animal studies suggest potential neurotrophic effects of Li
(57). In several brain regions including the cortex, Li affects multiple
cellular pathways including oxidative stress, apoptosis, inflammation, glial dysfunction, excitotoxicity, and mitochondrial stability
(58). Furthermore, Li increases expression of brain-derived neurotrophic factor and B-cell lymphoma-2, while inhibiting protein
kinase C and glycogen synthase kinase-3. It is currently unclear
which of these cellular actions may underlie the effects of Li on
brain volume. Further image analysis and corroborative histology
are currently underway to identify the cellular components and
mechanisms underlying both antipsychotic drugs and Li-induced
changes in brain volume.
Limitations of the current study should be noted. First, young
rats (spanning 10 –16 weeks of age), corresponding to late adolescence in humans, were used, not reflecting other age groups. Consequently, additional experimentation in younger and older animals is required. Second, there is a fundamental gap in our
knowledge of how chronic psychotropic drug treatment affects
cognition. Whereas chronic antipsychotic drug treatment induces
cognitive deficits, Li has been shown to improve cognition in rodents (54 –59). Third, we focused our studies on gray matter, because we did not detect any gross effect of antipsychotics on white
matter volume in our prior study (19) and human data suggest Li
does not affect white matter volume (3,4). Nevertheless, our data do
not preclude an effect of psychotropic drug treatment on white
matter microstructure, which may be observed using more sensitive imaging techniques, such as diffusion tensor imaging. Fourth,
www.sobp.org/journal
8 BIOL PSYCHIATRY 2012;xx:xxx
we used manual segmentation to measure brain volumes, a robust,
widely used method (19,25,59). However, it is prone to bias (although minimized by repeated measurements and blinding to subject treatment status) requires a priori hypotheses, and is relatively
insensitive to subtle morphologic change (60). Fourth, because of
the longitudinal nature of this in vivo study, postmortem analysis of
brain volume changes at Week 8 is lacking. Nevertheless, we have
previously confirmed HAL induced cortical volume change postmortem after 8 weeks of treatment (19).
In conclusion, our study offers a powerful model system for
further investigation of the effects of psychotropic drug treatment
on brain morphology. Our data are consistent with clinical studies
suggesting that antipsychotics may contribute to region-specific
brain volume decreases in schizophrenia patients, whereas Li induces brain volume increases in bipolar disorder patients. Notably,
our data suggest that the effects of HAL are dose-related and reversible, whereas some effects of Li are maintained following drug
withdrawal. Nonetheless, our studies were done in normal rats,
which do not capture the innate pathology of either schizophrenia
or bipolar disorder. Moreover, because the mechanism(s) of these
drug effects remain unknown, further studies are required, and one
should be cautious in drawing clinical inferences.
Strategic funding from the Medical Research Council (Grant Nos.
G0701748 [85253] and G1002198), which we thank for its generous
financial assistance, supported this study. We also thank the British
Heart Foundation for supporting the 7T magnetic resonance imaging
scanner at the King’s College London Preclinical imaging unit (KCLPIU).
JC acknowledges support from the Batten Disease Support and Research Association, Batten Disease Family Association, and The Natalie Fund, which provided the microscope setup. SCRW and WRC acknowledge support from the National Institute for Health Research
Biomedical Research Centre for Mental Health at the South London
and Maudsley National Health Service Foundation Trust and Institute
of Psychiatry, Kings College London, and the King’s College London
Centre of Excellence in Medical Engineering funded by the Wellcome
Trust and Engineering and Physical Sciences Research Council (Grant
No. WT 088641/Z/09/Z). We acknowledge the technical support of Miss
Lauren Heathcote M.Sc. and Dr. Po-Wah So (KCLPIU).
Some of the data (Figure 2) were previously published in part in
abstract form at the 24th European Congress of Neuropsychopharmacology, Paris, France (Paper No. CG11P-0457).
ACV, SN, WRC, MM, JDC, and SCRW report no biomedical financial
interests or potential conflicts of interest. Although we do not deem there
to be any conflicting interest, we declare to the editor and readers that
Professor Shitij Kapur has received grant support from AstraZeneca and
GlaxoSmithKline and has served as consultant and/or speaker for AstraZeneca, Bioline, BMS-Otsuka, Eli Lilly, Janssen (J&J), Lundbeck, NeuroSearch, Pfizer, Roche, Servier, and Solvay Wyeth in the past three years.
Supplementary material cited in this article is available online.
1. Ho BC, Andreasen NC, Ziebell S, Pierson R, Magnotta V (2011): Longterm antipsychotic treatment and brain volumes: A longitudinal study
of first-episode schizophrenia. Arch Gen Psychiatry 68:128 –137.
2. Lieberman JA, Tollefson GD, Charles C, Zipursky R, Sharma T, Kahn RS, et
al. (2005): Antipsychotic drug effects on brain morphology in first-episode psychosis. Arch Gen Psychiatry 62:361–370.
3. Lyoo IK, Dager SR, Kim JE, Yoon SJ, Friedman SD, Dunner DL, et al. (2010):
Lithium-induced gray matter volume increase as a neural correlate of
treatment response in bipolar disorder: A longitudinal brain imaging
study. Neuropsychopharmacology 35:1743–1750.
4. Moore GJ, Bebchuk JM, Wilds IB, Chen G, Manji HK (2000): Lithiuminduced increase in human brain grey matter. Lancet 356:1241–1242.
www.sobp.org/journal
A.C. Vernon et al.
5. Chakos MH, Lieberman JA, Bilder RM, Borenstein M, Lerner G, Bogerts B,
et al. (1994): Increase in caudate nuclei volumes of first-episode schizophrenic patients taking antipsychotic drugs. Am J Psychiatry 151:1430 –
1436.
6. Dazzan P, Morgan KD, Orr K, Hutchinson G, Chitnis X, Suckling J, et al.
(2005): Different effects of typical and atypical antipsychotics on grey
matter in first episode psychosis: the AESOP study. Neuropsychopharmacology 30:765–774.
7. Keshavan MS, Bagwell WW, Haas GL, Sweeney JA, Schooler NR,
Pettegrew JW (1994): Changes in caudate volume with neuroleptic
treatment. Lancet 344:1434.
8. Tost H, Braus DF, Hakimi S, Ruf M, Vollmert C, Hohn F, et al. (2010): Acute
D2 receptor blockade induces rapid, reversible remodeling in human
cortical-striatal circuits. Nat Neurosci 13:920 –922.
9. Cahn W, Hulshoff Pol HE, Lems EB, van Haren NE, Schnack HG, van der
Linden JA, et al. (2002): Brain volume changes in first-episode schizophrenia: A 1-year follow-up study. Arch Gen Psychiatry 59:1002–1010.
10. van Haren NE, Hulshoff Pol HE, Schnack HG, Cahn W, Brans R, Carati I, et
al. (2008): Progressive brain volume loss in schizophrenia over the
course of the illness: Evidence of maturational abnormalities in early
adulthood. Biol Psychiatry 63:106 –113.
11. van Haren NE, Schnack HG, Cahn W, van den Heuvel MP, Lepage C,
Collins L, et al. (2011): Changes in cortical thickness during the course of
illness in schizophrenia. Arch Gen Psychiatry 68:871– 880.
12. Moore GJ, Cortese BM, Glitz DA, Zajac-Benitez C, Quiroz JA, Uhde TW, et
al. (2009): A longitudinal study of the effects of lithium treatment on
prefrontal and subgenual prefrontal gray matter volume in treatmentresponsive bipolar disorder patients. J Clin Psychiatry 70:699 –705.
13. Sassi RB, Nicoletti M, Brambilla P, Mallinger AG, Frank E, Kupfer DJ, et al.
(2002): Increased gray matter volume in lithium-treated bipolar disorder patients. Neurosci Lett 329:243–245.
14. Yucel K, McKinnon MC, Taylor VH, Macdonald K, Alda M, Young LT, et al.
(2007): Bilateral hippocampal volume increases after long-term lithium
treatment in patients with bipolar disorder: A longitudinal MRI study.
Psychopharmacology (Berl) 195:357–367.
15. Yucel K, Taylor VH, McKinnon MC, Macdonald K, Alda M, Young LT, et al.
(2008): Bilateral hippocampal volume increase in patients with bipolar
disorder and short-term lithium treatment. Neuropsychopharmacology
33:361–367.
16. Kapur S, VanderSpek SC, Brownlee BA, Nobrega JN (2003): Antipsychotic dosing in preclinical models is often unrepresentative of the
clinical condition: A suggested solution based on in vivo occupancy.
J Pharmacol Exp Ther 305:625– 631.
17. McQuade R, Leitch MM, Gartside SE, Young AH (2004): Effect of chronic
lithium treatment on glucocorticoid and 5-HT1A receptor messenger
RNA in hippocampal and dorsal raphe nucleus regions of the rat brain.
J Psychopharmacol 18:496 –501.
18. O’Donnell KC, Gould TD (2007): The behavioral actions of lithium in
rodent models: leads to develop novel therapeutics. Neurosci Biobehav
Rev 31:932–962.
19. Vernon AC, Natesan S, Modo M, Kapur S (2011): Effect of chronic antipsychotic treatment on brain structure: A serial magnetic resonance
imaging study with ex vivo and postmortem confirmation. Biol Psychiatry 69:936 –944.
20. Quinn R (2005): Comparing rat’s to human’s age: How old is my rat in
people years? Nutrition 21:775–777.
21. Turrone P, Remington G, Kapur S, Nobrega JN (2003): The relationship
between dopamine D2 receptor occupancy and the vacuous chewing
movement syndrome in rats. Psychopharmacology (Berl) 165:166 –171.
22. Ferrie L, Young AH, McQuade R (2006): Effect of lithium and lithium
withdrawal on potassium-evoked dopamine release and tyrosine hydroxylase expression in the rat. Int J Neuropsychopharmacol 9:729 –735.
23. Scott J, Pope M (2002): Self-reported adherence to treatment with
mood stabilizers, plasma levels, and psychiatric hospitalization. Am J
Psychiatry 159:1927–1929.
24. Joint Formulary Committee (2011): British National Formulary (BNF),
61st ed. London: BMJ Publishing Group Ltd and Royal Pharmaceutical Society.
25. Vernon AC, Crum WR, Johansson SM, Modo M (2011): Evolution of
extra-nigral damage predicts behavioural deficits in a rat proteasome
inhibitor model of Parkinson’s disease. PLoS One 6:e17269.
26. Paxinos G, Watson C (2007): The Rat Brain in Stereotaxic Coordinates, 6th
ed. San Deigo, CA: Academic Press.
A.C. Vernon et al.
27. Wolf OT, Dyakin V, Vadasz C, de Leon MJ, McEwen BS, Bulloch K (2002):
Volumetric measurement of the hippocampus, the anterior cingulate
cortex, and the retrosplenial granular cortex of the rat using structural
MRI. Brain Res Brain Res Protoc 10:41– 46.
28. Kielar C, Maddox L, Bible E, Pontikis CC, Macauley SL, Griffey MA, et al.
(2007): Successive neuron loss in the thalamus and cortex in a mouse
model of infantile neuronal ceroid lipofuscinosis. Neurobiol Dis 25:150 –
162.
29. Gundersen HJ, Jensen EB (1987): The efficiency of systematic sampling
in stereology and its prediction. J Microsc 147:229 –263.
30. West MJ, Slomianka L, Gundersen HJ (1991): Unbiased stereological
estimation of the total number of neurons in thesubdivisions of the rat
hippocampus using the optical fractionator. Anat Rec 231:482– 497.
31. Thompson PM, Bartzokis G, Hayashi KM, Klunder AD, Lu PH, Edwards N,
et al. (2009): Time-lapse mapping of cortical changes in schizophrenia
with different treatments. Cereb Cortex 19:1107–1123.
32. Andersson C, Hamer RM, Lawler CP, Mailman RB, Lieberman JA (2002):
Striatal volume changes in the rat following long-term administration of
typical and atypical antipsychotic drugs. Neuropsychopharmacology 27:
143–151.
33. Chakos MH, Shirakawa O, Lieberman J, Lee H, Bilder R, Tamminga CA
(1998): Striatal enlargement in rats chronically treated with neuroleptic.
Biol Psychiatry 44:675– 684.
34. Kapur S, Zipursky R, Roy P, Jones C, Remington G, Reed K, et al. (1997):
The relationship between D2 receptor occupancy and plasma levels on
low dose oral haloperidol: A PET study. Psychopharmacology 131:148 –
152.
35. Wright IC, Rabe-Hesketh S, Woodruff PW, David AS, Murray RM, Bullmore ET (2000): Meta-analysis of regional brain volumes in schizophrenia. Am J Psychiatry 157:16 –25.
36. Kempton MJ, Stahl D, Williams SC, DeLisi LE (2010): Progressive lateral
ventricular enlargement in schizophrenia: A meta-analysis of longitudinal MRI studies. Schizophr Res 120:54 – 62.
37. Harrison PJ (1999): The neuropathology of schizophrenia. A critical review of the data and their interpretation. Brain 122:593– 624.
38. Monkul ES, Matsuo K, Nicoletti MA, Dierschke N, Hatch JP, Dalwani M, et
al. (2007): Prefrontal gray matter increases in healthy individuals after
lithium treatment: A voxel-based morphometry study. Neurosci Lett
429:7–11.
39. Hallahan B, Newell J, Soares JC, Brambilla P, Strakowski SM, Fleck DE, et
al. (2011): Structural magnetic resonance imaging in bipolar disorder:
An international collaborative mega-analysis of individual adult patient
data. Biol Psychiatry 69:326 –335.
40. Kempton MJ, Geddes JR, Ettinger U, Williams SC, Grasby PM (2008):
Meta-analysis, database, and meta-regression of 98 structural imaging
studies in bipolar disorder. Arch Gen Psychiatry 65:1017–1032.
41. Bearden CE, Thompson PM, Dalwani M, Hayashi KM, Lee AD, Nicoletti M,
et al. (2007): Greater cortical gray matter density in lithium-treated patients with bipolar disorder. Biol Psychiatry 62:7–16.
42. Bearden CE, Thompson PM, Dutton RA, Frey BN, Peluso MA, Nicoletti M,
et al. (2008): Three-dimensional mapping of hippocampal anatomy in
unmedicated and lithium-treated patients with bipolar disorder. Neuropsychopharmacology 33:1229 –1238.
43. Benes FM, Paskevich PA, Davidson J, Domesick VB (1985): The effects of
haloperidol on synaptic patterns in the rat striatum. Brain Res 329:265–
273.
BIOL PSYCHIATRY 2012;xx:xxx 9
44. Konradi C, Heckers S (2001): Antipsychotic drugs and neuroplasticity:
Insights into the treatment and neurobiology of schizophrenia. Biol
Psychiatry 50:729 –742.
45. Boonstra G, van Haren NE, Schnack HG, Cahn W, Burger H, Boersma M, et
al. (2011): Brain volume changes after withdrawal of atypical antipsychotics in patients with first-episode schizophrenia. J Clin Psychopharmacol 31:146 –153.
46. Andreasen NC, Nopoulos P, Magnotta V, Pierson R, Ziebell S, Ho BC
(2011): Progressive brain change in schizophrenia: A prospective longitudinal study of first-episode schizophrenia. Biol Psychiatry 70:672– 679.
47. Olabi B, Ellison-Wright I, McIntosh AM, Wood SJ, Bullmore E, Lawrie SM
(2011): Are there progressive brain changes in schizophrenia? A metaanalysis of structural magnetic resonance imaging studies. Biol Psychiatry 70:88 –96.
48. Edelfors S (1977): The influence of lithium on water binding ability,
consistency and macromolecules in the rat brain. Acta Pharmacol Toxicol (Copenh) 40:126 –133.
49. Phatak P, Shaldivin A, King LS, Shapiro P, Regenold WT (2006): Lithium
and inositol: Effects on brain water homeostasis in the rat. Psychopharmacology (Berl) 186:41– 47.
50. Kapur S, Mamo D (2003): Half a century of antipsychotics and still a
central role for dopamine D2 receptors. Prog Neuropsychopharmacol
Biol Psychiatry 27:1081–1090.
51. Samaha AN, Seeman P, Stewart J, Rajabi H, Kapur S (2007): “Breakthrough” dopamine supersensitivity during ongoing antipsychotic
treatment leads to treatment failure over time. J Neurosci 27:2979 –
2986.
52. Martins MR, Petronilho FC, Gomes KM, Dal-Pizzol F, Streck EL, Quevedo
J (2008): Antipsychotic-induced oxidative stress in rat brain. Neurotox
Res 13:63– 69.
53. Beaulieu JM, Tirotta E, Sotnikova TD, Masri B, Salahpour A, Gainetdinov
RR, et al. (2007): Regulation of Akt signaling by D2 and D3 dopamine
receptors in vivo. J Neurosci 27:881– 885.
54. Konopaske GT, Dorph-Petersen KA, Pierri JN, Wu Q, Sampson AR, Lewis
DA (2007): Effect of chronic exposure to antipsychotic medication on
cell numbers in the parietal cortex of macaque monkeys. Neuropsychopharmacology 32:1216 –1223.
55. Konopaske GT, Dorph-Petersen KA, Sweet RA, Pierri JN, Zhang W, Sampson AR, et al. (2008): Effect of chronic antipsychotic exposure on astrocyte and oligodendrocyte numbers in macaque monkeys. Biol Psychiatry 63:759 –765.
56. Selemon LD, Goldman-Rakic PS (1999): The reduced neuropil hypothesis: A circuit based model of schizophrenia. Biol Psychiatry 45:17–25.
57. Manji HK, Moore GJ, Chen G (2000): Lithium up-regulates the cytoprotective protein Bcl-2 in the CNS in vivo: a role for neurotrophic and
neuroprotective effects in manic depressive illness. J Clin Psychiatry 61(9
suppl):82–96.
58. Quiroz JA, Machado-Vieira R, Zarate CA Jr, Manji HK (2010): Novel insights into lithium’s mechanism of action: Neurotrophic and neuroprotective effects. Neuropsychobiology 62:50 – 60.
59. Piontkewitz Y, Assaf Y, Weiner I (2009): Clozapine administration in
adolescence prevents postpubertal emergence of brain structural pathology in an animal model of schizophrenia. Biol Psychiatry 66:1038 –
1046.
60. Ashburner J, Csernansky JG, Davatzikos C, Fox NC, Frisoni GB, Thompson PM (2003): Computer-assisted imaging to assess brain structure in
healthy and diseased brains. Lancet Neurol 2:79 – 88.
www.sobp.org/journal