Abnormal Trajectories of Neurodevelopment and Behavior Following In Utero Insult in the Rat

Abnormal Trajectories of Neurodevelopment and Behavior Following In Utero Insult in the Rat Yael Piontkewitz, Michal Arad, and Ina Weiner Background: Environmental or genetic disturbances of early brain development are suggested to underlie the pathophysiology of several adult-onset neuropsychiatric disorders. We traced the developmental trajectories of brain structural and behavioral abnormalities from adolescence to young adulthood in rats born to mothers exposed to the viral mimic polyriboinosinic-polyribocytidylic acid (poly-I:C) in pregnancy. Methods: Pregnant rats were injected on gestational day 15 with poly-I:C (4 mg/kg) or saline. Volumes of lateral ventricles, hippocampus, striatum, and prefrontal cortex in male and female offspring were assessed longitudinally at postnatal days 35, 46, 56, 70, and 90 using in vivo magnetic resonance imaging. At parallel time windows, groups of offspring from the same litters underwent behavioral testing (latent inhibition and amphetamine-induced activity) and magnetic resonance imaging (cross-sectional assessment). Results: The specific developmental trajectories of volumetric changes in both control and poly-I:C offspring were region-, age-, and sex-specific, but overall, poly-I:C offspring had smaller volumes of the hippocampus, striatum and prefrontal cortex, and larger ventricular volume. Structural pathology in different regions had different times of onset and was gradually accompanied by behavioral deficits, disrupted latent inhibition, and excessive amphetamine-induced activity. The onset of structural frontocortical and ventricular abnormalities and behavioral abnormalities was delayed in females. In both sexes, hippocampal and striatal volume reduction predated the appearance of behavioral abnormalities. Conclusions: Prenatal insult interferes with postnatal brain maturation, which in turn may result in behavioral abnormalities. Key Words: Amphetamine, developmental trajectories, latent inhibition, prenatal poly-I:C, rat, schizophrenia, structural brain changes any of the major neuropsychiatric disorders, including schizophrenia and affective disorders, have a typical age of onset in late adolescence/young adulthood, consistent with the notion that this is a period of brain development particularly vulnerable for the onset of psychopathology (1,2). Although the etiology of these disorders remains elusive, studies of potential genetic and environmental risk factors have suggested that disturbances of early brain development play a central role (3– 6). Consistent with this notion, genetic susceptibility factors identified for these disorders, such as Neuregulin-1 and Disrupted-in-Schizophrenia-1, have roles in neurodevelopment. Furthermore, prenatal and perinatal environmental adversities such as maternal malnutrition, stress, or infection have been associated with increased risk for these disorders (3,7–16). However, how early genetic and environmental brain insults may lead to adult-onset psychiatric disorders remains perplexing. One possibility is that early insult remains “silent” until adolescence, when compensatory changes are no longer sufficient. Alternatively, early developmental damage may lead to late symptom appearance by altering postnatal brain maturation (9,10,17–20). Neuroimaging studies have shown that schizophrenia and affective disorders are associated with structural brain changes that are evident at first episode or earlier and seem to become more severe as illness progresses, but whether these are progressive (reflecting late ongoing pathophysiological process) or static (reflecting early neurodevelopmental damage that arrests early in development) is controversial. The time course of these changes and their relationship to symptoms and

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From the Department of Psychology, Tel-Aviv University, Tel-Aviv, Israel. Address correspondence to Ina Weiner, Ph.D., Department of Psychology, Tel-Aviv University, Tel-Aviv 69978, Israel; E-mail: [email protected]. Received Sep 22, 2010; revised May 31, 2011; accepted Jun 9, 2011.

0006-3223/$36.00 doi:10.1016/j.biopsych.2011.06.007

to genetic/environmental risk factors remain to be established (16,21–25). Longitudinal imaging studies following high-risk individuals before and through transition to illness are imperative to clarify such questions (16,21–25). However, because of the methodological, diagnostic, and practical challenges facing such studies, few have been conducted, and answers are slow to emerge. Although animal models cannot recapitulate the full phenotypic spectrum of psychiatric disorders such as schizophrenia or depression, specific phenotypes such as developmental structural brain alterations that might be associated with the disorder can be recapitulated in “model rodents” with manipulations of genetic susceptibility or environmental risk factors. Such models can be informative for linking prenatal environmental or genetic disturbances with abnormalities of postnatal brain maturation and behavior (9,19,26 –32). Accordingly, here we used in vivo structural magnetic resonance imaging (MRI) to delineate the developmental trajectories of brain volumetric changes in rats born to mothers exposed to the viral mimic polyriboinosinicpolyribocytidylic acid (poly-I:C) in pregnancy, and associated behavioral abnormalities. Injection of pregnant rodents with poly-I:C has been shown to result in a wide spectrum of functional and neuropathological deficits in offspring (33– 41). We have recently shown that prenatal poly-I:C led to enlarged lateral ventricles (LV) and smaller hippocampal (HIP) volumes, accompanied by attentional deficit and hypersensitivity to the propsychotic drug amphetamine (AMPH), in adult offspring but had no adverse effects on these indices in adolescence. Furthermore, all abnormalities were prevented by the administration of atypical antipsychotic drugs (APDs) in adolescence (42,43). These results indicate that following prenatal poly-I:C exposure, there is a critical period between adolescence and early adulthood during which aberrant neurodevelopment leads to the emergence of behavioral abnormalities. Therefore, here we traced the developmental course of volumetric changes in HIP, LV, prefrontal cortex (PFC), and striatum (STR) as well as of the two behavBIOL PSYCHIATRY 2011;70:842– 851 © 2011 Society of Biological Psychiatry

Y. Piontkewitz et al. ioral phenomena, during this period. Our major hypotheses were that some structural changes would predate the manifestation of behavioral abnormalities and that there would be sex differences in the behavioral trajectories.

Methods and Materials Animals Male and female Wistar rats were housed 2 to 4 per cage under reversed-cycle lighting with ad libitum food and water (except for latent inhibition [LI] experiments described later in the article). Prenatal Poly-I:C Treatment Prenatal treatment was performed as described previously (33,44) (see also Supplement 1). On gestation day 15, pregnant dams were injected intravenously with poly-I:C (4 mg/kg/mL, Sigma, Rehovot, Israel) or saline under 3% isoflurane (Nicholas Piramal, Northumberland, United Kingdom) anesthesia. At birth, litters were standardized to five females and five males when possible. On postnatal day (PND) 21, the offspring were weaned and housed 2 to 4 to a cage by sex and litter. MRI Animals were scanned under inhalational isoflurane (1%–2%) anesthesia in 98% oxygen, with body temperature maintained at 37°C and respiration at 60 – 80 breath cycles/min. The scans were performed on a 7.0 T/30 cm (Bruker, Rheinstetten, Germany) with a volume coil for excitation and a rat quadrature coil for acquisition. Coronal T2-weighted images of the brain were acquired with rapid acquisition with relaxation enhancement (RARE) sequence, with repetition time ⫽ 3000 msec and echo time ⫽ 49 msec, RARE factor 8, 4 averages, field of view of 3 ⫻ 3 cm, matrix dimensions of 256 ⫻ 128 (zero filled to 256 ⫻ 256) and 18 coronal slices of 1 mm thickness without gap. The 18 coronal sections used for image analysis were taken perpendicular to a line connecting the superior end of the olfactory bulb with the anterior line of the cerebellum. The areas of the LV, HIP, PFC, STR, and the whole brain were obtained from the T2-weighted images with manual segmentation (Medical Image Analysis version 2.4, MATLAB). LV, HIPP, PFC, STR, and whole brain volumes were calculated by combining all slices where they appeared (approximately 2.20 to – 4.52 mm; –2.2 to – 6.2 mm; 1.2 to

BIOL PSYCHIATRY 2011;70:842– 851 843 – 4.2 mm; 2.2 to –1.2 mm; and 6.7 mm to –9.3 mm from bregma, respectively) and multiplied by slice thickness (1 mm). The anatomic borders used to draw the contour around the four regions are shown in Figure S1 in Supplement 1. High intrarater reliability as tested using intraclass Pearson correlation coefficient (icc) (riccs ⬎ .9) was obtained for all the MRI-derived volumetric assessments. Behavioral Phenotyping Behavioral phenotyping included LI and locomotor stimulating effect of the psychosis-inducing dopamine (DA) releaser AMPH. LI reflects the normal attentional capacity to ignore stimuli that were experienced as irrelevant in the past. Disrupted LI is considered relevant to psychotic symptoms because it is disrupted in AMPHtreated rodents and normal humans, in schizotypal persons, and in acutely psychotic schizophrenia patients (45). Excessively increased AMPH-induced activity (AIA) is considered to mimic subcortical DA hyperfunction and in particular the exacerbation of psychotic symptoms in response to AMPH in schizophrenia patients (39,46). Prenatal poly-I:C leads to LI disruption and elevated AIA in adult but not adolescent offspring (33,35). Latent Inhibition. LI was conducted as described previously (33) (see Supplement 1). After training to drink in the experimental chambers, rats underwent four stages given 24 hour apart. 1) Preexposure: with the bottle removed, preexposed (PE) rats received 40 tones (10 s, 80 dB, 2.8 kHz) 40 s apart, whereas non-preexposed (NPE) rats were confined to the chamber. 2) Conditioning: all rats received two tone–shock (.5 mA, 1 s) pairings given 5 min apart. 3) Lick retraining. 4) Test: rats were placed in the chambers with an access to the bottle. When the rats completed 75 licks, the tone was presented. Times to complete 25 licks before and after tone onset were recorded. LI is defined as shorter times to complete licks 76 to 100 after tone onset (weaker fear conditioning) of the PE compared with NPE rats. AMPH-Induced Activity. Activity was measured in dark gray boxes with cameras above each box connected to a computer running image analysis software that “grabbed” an image from each box every second (see Supplement 1). After 30-min habituation, rats were injected with AMPH (Sigma, St. Gallen, Switzerland; 1 mg/kg/mL), and replaced into the boxes for 60 min. Percentage of pixels that went from dark to light or vice versa from 1 s to the next

Figure 1. Experimental design used to trace the developmental trajectories of structural and behavioral changes from adolescence to adulthood in polyriboinosinic-polyribocytidylic acid (poly-I:C) or saline offspring. Pregnant rats were exposed to poly-I:C (4 mg/kg) or control treatment (saline) on GD 15. The resulting male and female offspring from both treatment conditions were assigned either to longitudinal or cross-sectional MRI and behavioral assessment. In longitudinal MRI, one group of offspring of poly-I:C or saline-injected dams was imaged repeatedly on PNDs 35, 46, 56, 70, and 90. For the cross-sectional part, five groups of male and female poly-I:C or saline offspring derived from the same litters were assigned to 5 time points. At each time point, each group was first tested in LI, with preexposure day coinciding with the days of longitudinal imaging (PNDs 35, 46, 56, 70, and 90). Five days later (2 days after the end of the LI procedure, PNDs 40, 51, 61, 75, and 95), about half of the rats were imaged and half examined in AIA. Because in longitudinal assessment, lateral ventricle volumes in poly-I:C females showed no change, an additional group of male and female offspring was imaged at PND 135. Data of AIA from the first time point (PND 40) were lost because of apparatus failure. AIA, amphetamine-induced activity; GD, gestational day; LI, latent inhibition; MRI, magnetic resonance imaging; PND, postnatal day.

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provided the measure of animal’s activity. One-second activity values ranged from 0% to approximately 7.5%. Experimental Design The study had two parts. In longitudinal imaging part, a group of male and female poly-I:C and saline offspring was imaged repeatedly on PNDs 35, 46, 56, 70, and 90. In the cross-sectional part, five cohorts of male and female poly-I:C or saline offspring derived from the same litters were tested in LI, with preexposure day coinciding with the days of longitudinal imaging, then imaged or tested in AIA on PNDs 40, 51, 61, 75, 95, or 135 (Figure 1). In all the experiments, each experimental group consisted of subjects derived from multiple independent litters (32 poly-I:C and 28 saline litters), with no more than 1 or 2 rats from the same litter in any of the experimental groups (see Table S1 in Supplement 1 for n per group). Data Analysis Data from longitudinal MRI and AIA were analyzed with twoway analyses of variance (ANOVAs; prenatal treatment ⫻ sex) with repeated-measure factors (age and blocks, respectively). For AIA data, separate two-way ANOVAs were used for spontaneous and AMPH-induced activity. LI and cross-sectional MRI data were analyzed with three-way ANOVAs (prenatal treatment ⫻ sex ⫻ preexposure and prenatal treatment ⫻ sex ⫻ age, respectively). Times to complete licks 76 to 100 were logarithmically transformed to allow analysis of variance. Significant interactions were followed by least significant difference post hoc comparisons.

Results Longitudinal Course of Structural Brain Changes Following Prenatal Poly-I:C Exposure In all four groups of offspring, HIP volume increased with age, but poly-I:C offspring of both sexes had smaller volume than saline offspring on all PNDs except PND 35 (Figure 2). ANOVA yielded main effects of prenatal treatment, sex, and age [F (1, 29) ⫽ 29.08, F (1,29) ⫽ 22.84, and F (4,116) ⫽ 26.35, respectively; all ps ⬍ .0001], and prenatal treatment ⫻ age interaction [F (4,116) ⫽ 12.04, p ⬍ .0001). Post hoc analyses of the interaction confirmed significant differences in HIP volume between polyI:C and saline offspring on PNDs 46, 56, 70 and 90 (ps ⬍ .001) but not PND 35 (Figure 2 inset). In all four groups of offspring, LV volume increased with age. Abnormal LV volume expansion was sex-specific. In male poly-I:C offspring, divergence from controls began at PND 56, whereas there were no differences in LV volume between female offspring (Figure 3). ANOVA yielded main effects of prenatal treatment, sex, and age [F (1,29) ⫽ 12.68, F (1,29) ⫽ 6.59, and F (4,116) ⫽ 58.21, respectively; all ps ⬍ .001], and prenatal treatment ⫻ sex ⫻ age interaction [F (4,116) ⫽ 4.85, p ⬍ .002]. Post hoc comparisons confirmed differences between saline and poly-I:C male offspring at PNDs 56, 70, and 90 (ps ⬍ .02) but not PNDs 35 and 46 and no differences between female offspring across the five time points. PFC volume increased between PND 35– 46 to reach a plateau in all four groups of offspring and declined in the period between PNDs 56 –90 depending on prenatal treatment and sex. Volume decline began on PND 56 in poly-I:C males, PND 70 in saline males and poly-I:C females, and was absent in control females. Volume reduction was larger in poly-I:C offspring compared with controls. Poly-I:C males had smaller PFC volume than controls at PND 70 and PND 90, whereas poly-I:C females had smaller volume than controls at PND 90 (Figure 4). ANOVA yielded main effects of prenatal treatment, sex, and age [F(1,29) ⫽ 6.10, F(1,29) ⫽ 7.81, and F(4,116) ⫽ 103.99, respectively; all www.sobp.org/journal

Figure 2. Longitudinal course of hippocampal volume changes between adolescence and adulthood in male and female polyriboinosinic-polyribocytidylic acid (poly-I:C) or saline offspring. (A) Representative T2-weighted images at the level of the hippocampus (HIP) from a male saline or poly-I:C offspring imaged repeatedly on postnatal days (PNDs) 35, 46, 56, 70, and 90, at each PND. (B) Representative T2-weighted images at the level of the HIP from a female saline or poly-I:C offspring imaged repeatedly at the five time points, at each PND. (C) Mean ⫾ SEM HIP volume of male and female (Fem) saline or poly-I:C offspring at each of the five time points (n per group ⫽ 7–9). The inset depicts the prenatal treatment ⫻ age interaction. *Significant difference between poly-I:C and saline offspring (all ps ⬍ .001) as revealed in post hoc analyses.

ps ⬍ .03), and prenatal treatment ⫻ sex ⫻ age interaction [F(4,116) ⫽ 2.6, p ⬍ .04). Post hoc comparisons yielded differences between saline and poly-I:C males at PNDs 35, 70, and 90, and between saline and poly-I:C females at PND 90 (all ps ⬍ .05). Striatal volume increased with age in both groups of male offspring between PNDs 35–70 and then decreased, and only increased in both groups of female offspring between PNDs 35–90, but poly-I:C offspring of both sexes had smaller volume on all PNDs (Figure 5). ANOVA yielded main effects of prenatal treatment, sex, and age [F(1,30) ⫽ 27.20, F(1,30) ⫽ 56.54, and F(4,120) ⫽ 22.41, respectively; all ps ⬍ .0001], and interaction between age ⴛ sex [F(4,120) ⫽ 13.14, p ⬍ .0001].

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Figure 3. Longitudinal course of lateral ventricle (LV) volume changes between adolescence and adulthood in male and female polyriboinosinicpolyribocytidylic acid (poly-I:C) or saline offspring. (A) Representative T2weighted images at the level of the LV from a male saline or poly-I:C offspring imaged repeatedly on postnatal days (PNDs) 35, 46, 56, 70, and 90 at each PND. (B) Representative T2-weighed images at the level of the LV from a female saline or poly-I:C offspring imaged repeatedly at the five time points at each PND. (C) Mean ⫾ SEM LV volume of male and female (Fem) saline or poly-I:C offspring at each of the five time points (n per group ⫽ 7–9). *Significant difference between poly-I:C and saline male offspring (all ps ⬍ .02) as revealed in post hoc analyses.

There were no differences in total brain volume between the four groups at PND 35 or PND 95 [main effect of age only F (1,30) ⫽ 34.98, p ⬍ .0001; Table 1]. For cross-sectional assessment of volumetric changes between PNDs 40⫺135 see Supplement 1. Developmental Trajectory of Behavioral Changes between Adolescence and Adulthood Following Prenatal Poly-I:C Exposure Latent inhibition. Each LI experiment included eight groups in a 2 ⴛ 2 ⴛ 2 factorial design (prenatal treatment ⴛ sex ⴛ preexposure). In all the experiments, the eight groups did not differ in times to complete licks 51 to 75 before tone onset (ps ⬎ .05). LI,

namely, lower suppression of drinking of the PE compared with NPE rats, was present in all groups of offspring on PND 35 [main effect of preexposure F (1,47) ⫽ 98.46, p ⬍ .0001], PND-46 [main effect of preexposure F (1,49) ⫽ 84.35, p ⬍ .0001], and PND 56 [main effect of preexposure F (1,50) ⫽ 69.91, p ⬍ .0001]. On PND 70, LI was present in saline offspring of both sexes as well as in poly-I:C females but not in male poly-I:C offspring (preexposure ⴛ prenatal treatment ⴛ sex interaction, F (1,49) ⫽ 5.17, p ⬍ .05], and significant differences between PE and NPE groups in saline offspring of both sexes and in poly-I:C females (ps ⬍ .01) but not in poly-I:C males in post hoc comparisons). On PND 90, LI was present in female and male saline offspring but absent in female and male poly-I:C offspring (preexposure ⴛ prenatal treatment interaction [F (1,54) ⫽ 40.48, p ⬍ .0001], and significant differences between PE and NPE groups in the saline offspring of both sexes (ps ⬍ .01) but not in the poly-I:C offspring of both sexes, in post hoc comparisons (Figure 6A; see Supplement 1 for full ANOVA). Spontaneous and AMPH-Induced Activity. Each AIA experiment included four groups (prenatal treatment ⴛ sex). Data of the first time point (PND 40) were lost because of apparatus failure. In all the experiments except the last (PND 95), the four groups did not differ in their spontaneous activity (blocks 1– 6; main effect of blocks, all ps ⬍ .0001). On PND 51, there were no differences in AIA between saline and poly-I:C offspring [main effect of blocks F (11,275) ⫽ 48.97, p ⬍ .0001]. On PND 61 there was no difference between saline and poly-I:C female offspring, but male poly-I:C offspring showed higher AIA than their controls on blocks 8 and 10 through 18 [prenatal treatment ⴛ sex ⴛ blocks interaction, F (11,275) ⫽ 3.47, p ⬍ .0001, and significant differences in post hoc comparisons, ps ⬍ .01). On PND 75, there was no difference in AIA between saline and poly-I:C female offspring, but poly-I:C males had lower AIA than controls on blocks 8 through 10 [prenatal treatment ⴛ sex ⴛ blocks interaction, F (11,264) ⫽ 4.18, p ⬍ .0001, and significant differences in post hoc comparisons, ps ⬍ .01]. On PND 95, both male and female poly-I:C offspring exhibited higher AIA than their controls on blocks 8 through 18 [prenatal treatment ⴛ blocks interaction, F (11,275) ⫽ 1.84, p ⬍ .05, p ⬍ .0001, and significant differences in post hoc comparisons, ps ⬍ .05). On this PND, both male and female poly-I:C offspring exhibited also higher spontaneous activity [prenatal treatment ⴛ blocks interaction, F(5,125) ⫽ 3.25, p ⬍ .01, and significant differences in post hoc comparisons, ps ⬍ .05; Figure 6B; see Supplement 1 for full ANOVA results].

Discussion This study provides the first in vivo longitudinal characterization of volumetricandbehavioralchangesoccurringasaconsequenceofinutero insult in rats of both sexes. Main findings include the following: 1) prenatal exposure to the viral mimic poly-I:C leads to abnormal postnatal trajectories of neurodevelopment, 2) there are conspicuous sex differences in both structural and behavioral trajectories, and 3) low striatal volume and HIP volume loss in adolescence predate the appearance of behavioral abnormalities in both sexes. In the control offspring, longitudinal volumetric changes spanning from young adolescence through young adulthood were region- and sex-specific. In males, PFC and STR trajectories were Ushaped, with volumes expanding between PND 35–70 followed by volume reduction, whereas no volume reduction was seen in female PFC and STR (such reductions would presumably become evident in females had we imaged at later PNDs). HIP and LV volumes increased with age in both sexes. These trajectories are broadly consistent with those reported in humans and animals during comparable time spans (47–50). www.sobp.org/journal

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Figure 4. Longitudinal course of prefrontal cortex (PFC) volume changes between adolescence and adulthood in male and female polyriboinosinicpolyribocytidylic acid (poly-I:C) or saline offspring. For PFC, we show representative images only for two PNDs at which significant differences between offspring of poly-I:C and saline were found—namely postnatal day (PND) 70 for males and PND 90 for females. (A) Four representative T2-weighted images at the level of the cingulate cortex from a male saline or poly-I:C offspring imaged repeatedly on PNDs 35, 46, 56, 70, and 90, at PND 70. (B) Four representative T2 -weighted images at the level of the cingulate cortex from a female saline or poly-I:C offspring imaged repeatedly on PNDs 35, 46, 56, 70, and 90, at PND-90. In both panel A and B, the left images show an unmarked slice at approximately –.2 mm from Bregma, whereas the right images show on the same slice the manual outlining (white line) on the left side and a right unmarked side. (C) Mean ⫾ SEM PFC volume of male and female (Fem) saline or poly-I:C offspring at each of the five PNDs at which they were imaged (n per group ⫽ 7–9). *Significant difference between male poly-I:C and saline offspring (p ⬍ .02). **Significant difference between male and female poly-I:C and saline offspring (all ps ⬍ .05) as revealed in post hoc analyses.

Prenatal poly-I:C did not change the overall shape of the trajectories but led to maturation- and sex-dependent volumetric deviations in all four trajectories, with volume reduction in HIP, PFC, and STR and volume increase in LV compared with controls. HIP volume loss occurred in both sexes in adolescence (PND 35– 46), in parallel to volume increase in controls. After that, HIP volume increased but remained consistently smaller than that of controls. This pattern reveals that smaller hippocampal volume in adult poly-I:C offspring does not represent progressive volume reduction but rather a disruption of hippocampal volume expansion that normally occurs between adolescence and adulthood. PFC volume loss occurred in both sexes in young adulthood, preceding that of controls, but was delayed in poly-I:C females, paralleling the normally occurring delay in PFC volume reduction in females compared with males. Thus, PFC volume loss in males seems best described as accelerated volume loss that normally takes place in late adolescence/early adulthood (cross-sectional imaging showed PFC reduction in polyI:C females at PNDs 95 and135). Smaller STR volume was present in both sexes by PND 35 and remained static throughout all the PNDs. LV volume expansion differed dramatically between the sexes. In poly-I:C males, LV volume increased from PND 56 until PND 90 compared with controls, but no increase in LV volume was seen in poly-I:C females compared with controls during the same time span (cross-sectional imaging showed LV expansion in females at PND 135). Behaviorally, both male and female poly-I:C offspring exhibited selective attention deficit as manifested in loss of LI and excessive response to AMPH in adulthood but not in adolescence, as has been shown previously (33). However, there were conspicuous sex differences in the times of emergence of these abnormalities. In poly-I:C www.sobp.org/journal

males, higher AIA was first seen at PND-61, and disrupted LI emerged at PND 70. In contrast, both disrupted LI and AIA were delayed until PND 95 in poly-I:C females (see Supplement 1 for further discussion). Taken together, our findings show that prenatal insult affects postnatal brain development and adult behavior. Notably, it is clear from our data that the volumetric abnormalities in poly-I:C offspring are best described as deviations from normal trajectories of development. The specific trajectories of volumetric abnormalities, like those of normal trajectories, are region-, sex-, and developmental window-specific, and in addition differ in their time of onset, suggesting that prenatal insult interacts with multiple maturational processes, normal and/or abnormal, to precipitate long-term structural abnormalities. Furthermore, critical developmental aberrations, specifically in temporolimbic and frontocortical but possibly in additional regions given the progressively increasing LV volume, do take place in adolescence/young adulthood, consistent with the notion that this is a critical period of neurodevelopment vulnerable for the development of neuropathology (51–53). It is important to note that although volumetric changes transpiring in individual regions (e.g., STR and HIPP after PND 46) are not progressive, brain pathology in the brains of poly-I:C offspring is progressive in the sense that neurodevelopment of more regions becomes affected with maturation. The cellular processes underlying the structural changes in polyI:C offspring remain to be investigated. Disrupted neurogenesis may play a role in HIP volume loss, because this process normally continues within the HIP into adolescence and adulthood and may contribute to HIP volume gain (54) but is suppressed in adolescence following prenatal poly-I:C exposure (28,55). Volume reductions in the PFC and STR may be related to abnormally accelerated matura-

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Figure 5. Longitudinal course of striatal volume changes between adolescence and adulthood in male and female polyriboinosinic-polyribocytidylic acid (poly-I:C) or saline offspring. (A) Representative T2-weighted images at the level of the striatum from a male saline or poly-I:C offspring imaged repeatedly on postnatal days (PNDs) 35, 46, 56, 70, and 90, at each PND. (B) Representative T2-weighted images at the level of the striatum from a female saline or poly-I:C offspring imaged repeatedly at the five time points at each PND. (C) Mean ⫾ SEM striatum volume of male and female (Fem) saline or poly-I:C offspring at each of the five time points (n per group ⫽ 8 –9). Analysis of variance yielded main effects of prenatal treatment and age (ps ⬍ .0001).

tional processes that normally lead to volumetric reductions such as synaptic pruning (51,53). Whatever the mechanisms, it appears that the late progressive pathophysiologic process may underlie the emergence of behavioral abnormalities. Furthermore, we hypothesized that the development of brain structural changes would predate behavioral changes. A comparison of the behavioral and volumetric trajectories (see Table 2) shows this to be the case for HIP and STR but not for PFC and LV, suggesting that in poly-I:C offspring, HIP volume loss in adolescence superimposed on preexisting shrunken striatal volume, is a marker for the emergence of behavioral pathology. Importantly, although HIP and STR perturbations can produce increased AIA and LI loss (56,57), different onset times of these deficits suggest that age- and sex-dependent matu-

rational processes in other brain systems, which either interact with HIP and/or STR pathology or must themselves reach a specific developmental stage, are required for their manifestations. Changes in the PFC can be one such process because the emergence of structural pathology in the PFC coincided with loss of LI and because interactions of PFC with HIP and/or striatal function are well documented (57,58). Maturational changes in the dopaminergic system is an additional likely candidate because both AIA and LI disruption are mediated by striatal hyperdopaminergia (40,45), and DA dysfunction is well documented in poly-I:C offspring (31,33). Because perturbations of both HIP and PFC lead to elevated striatal DA activity (58,59), it can be speculated that subcortical DA hyperfunction in poly-I:C rats is progressively escalating postnatally in response to disrupted temporolimbic and later frontocortical input to the DA system to produce age-dependent emergence of behavioral abnormalities. The delayed emergence of structural and behavioral deficits in female poly-I:C offspring could reflect neuroprotective effects of estrogen (60,61). However, our data suggest that delayed volume loss in females compared with males is characteristic of normal developmental trajectories. This suggests that estrogen does not play a neuroprotective role following prenatal insult but is involved in sex-dependent differences in normal brain development (e.g., Sisk and Zehr [62]), which in turn affect brain response to prenatal insults. Estrogen could confer direct protection from DA elevation since we have recently shown that estradiol prevents LI disruption by AMPH in normal adult female and male rats (63, 64). Since levels of estradiol peak in female rats in adolescence (52), it could protect poly-I:C females behaviorally. Taken together, our findings suggest that prenatal poly-I:C induced insult to the fetal brain leads to aberrant temporolimbic and frontocortical neurodevelopment evolving during adolescence/ young adulthood, which interacts with earlier striatal abnormality as well as other maturational processes, to lead to the emergence of behavioral abnormalities. Although assessment of additional behaviors is required to substantiate this suggestion, it is supported by the fact that in females, both structural and behavioral abnormalities were delayed, as well as by our previous findings that pharmacologic treatment prevented both structural (HIP and LV) and behavioral abnormalities (42,43). Although extrapolation from animal data to clinical disorders must be made with extreme caution, our data may have relevance for adult-onset neuropsychiatric disorders in which neurodevelopTable 1. Total Brain Volume in Adolescence and Adulthood Prenatal Treatment Saline Male/adolescence Male/adulthood Female/adolescence Female/adult Poly I:C Male/adolescence Male/adulthood Female/adolescence Female/adult

Brain Volume (mm3, mean ⫾ SEM) 1174.2 ⫾ 19.6a 1316.1 ⫾ 46.5 1180.9 ⫾ 29.0a 1331.1 ⫾ 22.0 1148.9 ⫾18.4a 1309.2 ⫾ 44.3 1185.7 ⫾10.4a 1271.4 ⫾ 25.4

Mean ⫾ SEM brain volume (mm3) in male and female saline- or polyriboinosinic-polyribocytidylic acid (poly-I:C) offspring imaged at adolescence (postnatal day 35) and adulthood (postnatal day 90). Brain volumes increased with age, but no significant differences were found between polyI:C and saline offspring or between females and males. a Significant difference between adolescent and adult brains.

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Figure 6. The developmental course of behavioral changes between adolescence and adulthood in female and male saline or polyriboinosinic-polyribocytidylic acid (poly-I:C) offspring. (A) Latent inhibition (LI). Five groups of offspring were tested at five time windows between adolescence and adulthood (postnatal days [PNDs] 30 –38, 41– 49, 51–59, 65–73, or 85–93), with preexposure day coinciding with the days of longitudinal imaging (PND 35, 46, 56, 70, or 90, respectively; n per group ⫽ 6 – 8). Depicted are mean ⫾ SEM times (logarithmically transformed) to complete 25 licks in the presence of a tone that was previously paired with shock in the female and male poly-I:C or saline offspring tested at each of the time windows. In each experiment, preexposed (PE) rats received 40 nonreinforced tone presentations before tone-shock conditioning, whereas non-preexposed (NPE) rats did not receive any tones. LI is manifested as shorter log times to complete 25 licks after tone onset of the PE compared with the NPE group. LI was present in the saline offspring of both sexes at each of the time windows. Male poly-I:C offspring showed disruption of LI at PND 70 and PND 90 windows, whereas female poly-I:C offspring showed disruption of LI only at the PND 90 window. *Significant difference between the times of PE compared with NPE groups to complete 25 licks after tone onset (i.e., LI; ps ⬍ .01). (B) Amphetamine-induced activity (AIA): four groups of male and female poly-I:C or saline offspring were tested at four time points between adolescence and adulthood (2 days after LI; PND 51, 61, 75, or 95; n per group 7– 8). Depicted are mean ⫾ SEM activity counts, in 5-min blocks, before (blocks 1– 6) and after (blocks 7–18) amphetamine (amph) injection in the female and male poly-I:C or saline offspring tested at each of the four time points. Male poly-I:C offspring showed higher AIA than controls on PND 61, which disappeared on PND 75 because of increased AIA in controls and re-appeared on PND 95. Female offspring showed higher AIA only on PND 95. On the latter PND, both sexes also showed increased spontaneous activity. *Significant differences between poly-I:C-and saline offspring (ps ⬍ .05) as revealed in post hoc analyses.

mental factors are believed to play a role. In particular, it has been suggested that prodromal stages of schizophrenia and transition to frank psychosis may reflect abnormal developmental trajectories of disturbed brain maturation (18 –20,65). Accordingly, although the

specific regions and temporal course are still debated, longitudinal structural neuroimaging studies in genetic and clinical high-risk individuals have described volumetric reductions in frontocortical and temporolimbic regions that occur before and through transi-

Table 2. First Emergence of Structural and Behavioral Abnormalities in Poly-I:C Offspring: Summary of Longitudinal and Cross-Sectional Assessments Poly I:C Offspring

Assessment

HIP 2

LV 1

PFC 2

STR 2

AIA 1

LI 2

Male Male Female Female

Longitudinal Cross Longitudinal Cross

PND 46 PND 51 PND 46 PND 51

PND 56 PND 61 — PND 135

PND 70a PND 51 PND 90 PND 95

PND 35 PND 40 PND 35 PND 40

— PND 61 — PND 95

— PND 75 — PND 95

In both longitudinal and cross-sectional assessment, low STR volume was first seen in early adolescence (PND 35 and PND 40, respectively), and reduction of HIP volume emerged in late adolescence (PND 46 and PND 51, respectively), predating behavioral abnormalities (loss of LI and excessive AMPH induced activity) as well as abnormal LV expansion and PFC volume loss. The time of first appearance of the latter changes was sex-dependent, delayed in females. LV dilation emerged in male offspring in proximity to behavioral abnormalities and in female offspring only after the emergence of behavioral abnormalities. Postpubertal PFC volume decline was associated with loss of LI in males and with both behavioral abnormalities in females, suggesting that this late volume loss exerts important influence on the behavioral manifestations. 1 increase; 2 reduction; AIA, amphetamine-induced activity; HIP, hippocampus; LI, latent inhibition; LV, lateral ventricles; PFC, prefrontal cortex; PND, postnatal day; STR, striatum. a Lower PFC volume was also found in males at PND 35. However, because in contrast to all the other volumetric reductions that continued across next PNDs, early PFC volume reduction totally “recovered,” increasing to reach control volume between PND 35 and PND 46, we chose not to treat it as a predictor.

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Y. Piontkewitz et al. tion to psychosis (66 –70). In addition, recent studies reported that smaller striatal volumes are present before onset of psychosis (71) and that abnormal hippostriatal and frontostriatal interactions may be risk markers for transition to psychosis (72,73). Unfortunately, few longitudinal studies have been conducted, and establishing the longitudinal course of the development of structural brain abnormalities underlying progression to full-blown psychosis has been elusive (1,74). Given that prenatal infection or cytokine exposure is most closely associated with increased risk for schizophrenia (7,36,75) and the resemblance of many neuropathological and behavioral findings in the offspring of dams exposed to infection or immune stimulation to those documented in schizophrenia (29,35,39,40,76 – 80), abnormal developmental trajectories induced by prenatal poly-I:C exposure could be suitable for modeling developmental brain abnormality in schizophrenia. In addition, to the best of our knowledge, this is the first animal analogue of the well-documented later onset of symptoms in women with schizophrenia compared to men (81). Clearly, longitudinal characterization of additional structural changes occurring after prenatal poly-I:C as well as of additional behavioral manifestations, are necessary to link our data to schizophrenia. In particular, behavioral abnormalities in additional domains considered relevant to schizophrenia (e.g., disrupted working memory or social interaction) should be assessed and would likely exhibit different developmental trajectories and different relationships with the structural trajectories. Second, our imaging data must be supplemented with the assessment of underlying cellular and molecular processes for comprehensive phenotyping. Of particular interest would be to discern the degree to which volumetric changes are related to altered developmental molecular and cellular mechanisms that have already been identified following prenatal poly-I:C and other environmental or genetic perturbations (26 –31,55,76,77). In vivo rodent imaging provides a robust translational measure, and its combination with neurobiochemical and behavioral analyses in animals may provide a powerful technique for clarifying the nature of brain maturational abnormalities caused by various early genetic or environmental insults. This work was partially supported by the United States–Israel Binational Science Foundation (BSF Grant No. 2007188). The magnetic resonance imaging scanner used in this study was purchased with a grant from the Israel Science Foundation and operated under the Raymond and Beverly Sackler Center for Biophysics, Tel Aviv University, and the Alfredo Federico Strauss Center for Computational Neuro-Imaging, Tel Aviv University. MA is currently affiliated with the Department of Psychiatry, University of Maryland School of Medicine, Baltimore, Maryland. The authors report no biomedical financial interests or potential conflicts of interest. Supplementary material cited in this article is available online. 1. Gogtay N, Vyas NS, Testa R, Wood SJ, Pantelis C (2011): Age of onset of schizophrenia: Perspectives from structural neuroimaging studies. Schizophr Bull 37:504 –513. 2. Paus T, Keshavan M, Giedd JN (2008): Why do many psychiatric disorders emerge during adolescence? Nat Rev Neurosci 9:947–957. 3. Mittal VA, Ellman LM, Cannon TD (2008): Gene-environment interaction and covariation in schizophrenia: The role of obstetric complications. Schizophr Bull 34:1083–1094. 4. Lewis DA, Levitt P (2002): Schizophrenia as a disorder of neurodevelopment. Annu Rev Neurosci 25:409 – 432. 5. Savitz J, Drevets WC (2009): Bipolar and major depressive disorder: Neuroimaging the developmental-degenerative divide. Neurosci Biobehav Rev 33:699 –771.

BIOL PSYCHIATRY 2011;70:842– 851 849 6. Tenyi T, Trixler M, Csabi G (2009): Minor physical anomalies in affective disorders. A review of the literature. J Affect Disord 112:11–18. 7. Brown AS, Derkits EJ (2010): Prenatal infection and schizophrenia: A review of epidemiologic and translational studies. Am J Psychiatry 167: 261–280. 8. Harrison PJ, Weinberger DR (2005): Schizophrenia genes, gene expression, and neuropathology: On the matter of their convergence. Mol Psychiatry 10:40 – 68. 9. Insel TR (2010): Rethinking schizophrenia. Nature 468:187–193. 10. Thompson BL, Levitt P (2010): The clinical-basic interface in defining pathogenesis in disorders of neurodevelopmental origin. Neuron 67: 702–712. 11. Fumagalli F, Molteni R, Racagni G, Riva MA (2007): Stress during development: Impact on neuroplasticity and relevance to psychopathology. Prog Neurobiol 81:197–217. 12. Weinstock M (2008): The long-term behavioural consequences of prenatal stress. Neurosci Biobehav Rev 32:1073–1086. 13. Heim C, Nemeroff CB (2001): The role of childhood trauma in the neurobiology of mood and anxiety disorders: Preclinical and clinical studies. Biol Psychiatry 49:1023–1039. 14. Machon RA, Mednick SA, Huttunen MO (1997): Adult major affective disorder after prenatal exposure to an influenza epidemic. Arch Gen Psychiatry 54:322–328. 15. Sacker A, Done DJ, Crow TJ, Golding J (1995): Antecedents of schizophrenia and affective illness. Obstetric complications. Br J Psychiatry 166:734 –741. 16. Sanches M, Keshavan MS, Brambilla P, Soares JC (2008): Neurodevelopmental basis of bipolar disorder: A critical appraisal. Prog Neuropsychopharmacol Biol Psychiatry 32:1617–1627. 17. Thompson BL, Levitt P (2010): Now you see it, now you don’t—Closing in on allostasis and developmental basis of psychiatric disorders. Neuron 65:437– 439. 18. Cannon TD, van Erp TG, Bearden CE, Loewy R, Thompson P, Toga AW, et al. (2003): Early and late neurodevelopmental influences in the prodrome to schizophrenia: Contributions of genes, environment, and their interactions. Schizophr Bull 29:653– 669. 19. Jaaro-Peled H, Hayashi-Takagi A, Seshadri S, Kamiya A, Brandon NJ, Sawa A (2009): Neurodevelopmental mechanisms of schizophrenia: Understanding disturbed postnatal brain maturation through neuregulin1-ErbB4 and DISC1. Trends Neurosci 32:485– 495. 20. Pantelis C, Yucel M, Bora E, Fornito A, Testa R, Brewer WJ, et al. (2009): Neurobiological markers of illness onset in psychosis and schizophrenia: The search for a moving target. Neuropsychol Rev 19:385–398. 21. Smieskova R, Fusar-Poli P, Allen P, Bendfeldt K, Stieglitz RD, Drewe J, et al. (2010): Neuroimaging predictors of transition to psychosis—A systematic review and meta-analysis. Neurosci Biobehav Rev 34:1207–1222. 22. Rao U, Chen LA, Bidesi AS, Shad MU, Thomas MA, Hammen CL (2010): Hippocampal changes associated with early-life adversity and vulnerability to depression. Biol Psychiatry 67:357–364. 23. Berk M, Kapczinski F, Andreazza AC, Dean OM, Giorlando F, Maes M, et al. (2011): Pathways underlying neuroprogression in bipolar disorder: Focus on inflammation, oxidative stress and neurotrophic factors. Neurosci Biobehav Rev 35:804 – 817. 24. Bora E, Fornito A, Pantelis C, Yucel M (2011): Gray matter abnormalities in major depressive disorder: A meta-analysis of voxel based morphometry studies [published online ahead of print April 19]. J Affect Disord. 25. Bora E, Fornito A, Yucel M, Pantelis C (2010): Voxelwise meta-analysis of gray matter abnormalities in bipolar disorder. Biol Psychiatry 67:1097– 1105. 26. Niwa M, Kamiya A, Murai R, Kubo K, Gruber AJ, Tomita K, et al. (2010): Knockdown of DISC1 by in utero gene transfer disturbs postnatal dopaminergic maturation in the frontal cortex and leads to adult behavioral deficits. Neuron 65:480 – 489. 27. Baharnoori M, Brake WG, Srivastava LK (2009): Prenatal immune challenge induces developmental changes in the morphology of pyramidal neurons of the prefrontal cortex and hippocampus in rats. Schizophr Res 107:99 –109. 28. Cui K, Ashdown H, Luheshi GN, Boksa P (2009): Effects of prenatal immune activation on hippocampal neurogenesis in the rat. Schizophr Res 113:288 –297. 29. Fatemi SH, Reutiman TJ, Folsom TD, Huang H, Oishi K, Mori S, et al. (2008): Maternal infection leads to abnormal gene regulation and brain atrophy in

www.sobp.org/journal

850 BIOL PSYCHIATRY 2011;70:842– 851

30.

31.

32.

33.

34.

35.

36. 37. 38.

39. 40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

mouse offspring: Implications for genesis of neurodevelopmental disorders. Schizophr Res 99:56 –70. Romero E, Guaza C, Castellano B, Borrell J (2010): Ontogeny of sensorimotor gating and immune impairment induced by prenatal immune challenge in rats: Implications for the etiopathology of schizophrenia. Mol Psychiatry 15:372–383. Vuillermot S, Weber L, Feldon J, Meyer U (2010): A longitudinal examination of the neurodevelopmental impact of prenatal immune activation in mice reveals primary defects in dopaminergic development relevant to schizophrenia. J Neurosci 30:1270 –1287. Abazyan B, Nomura J, Kannan G, Ishizuka K, Tamashiro KL, Nucifora F, et al. (2010): Prenatal interaction of mutant DISC1 and immune activation produces adult psychopathology. Biol Psychiatry 68:1172–1181. Zuckerman L, Rehavi M, Nachman R, Weiner I (2003): Immune activation during pregnancy in rats leads to a postpubertal emergence of disrupted latent inhibition, dopaminergic hyperfunction, and altered limbic morphology in the offspring: A novel neurodevelopmental model of schizophrenia. Neuropsychopharmacology 28:1778 –1789. Ozawa K, Hashimoto K, Kishimoto T, Shimizu E, Ishikura H, Iyo M (2006): Immune activation during pregnancy in mice leads to dopaminergic hyperfunction and cognitive impairment in the offspring: A neurodevelopmental animal model of schizophrenia. Biol Psychiatry 59:546 – 554. Meyer U, Feldon J, Schedlowski M, Yee BK (2005): Towards an immunoprecipitated neurodevelopmental animal model of schizophrenia. Neurosci Biobehav Rev 29:913–947. Patterson PH (2007): Neuroscience. Maternal effects on schizophrenia risk. Science 318:576 –577. Meyer U, Feldon J (2010): Epidemiology-driven neurodevelopmental animal models of schizophrenia. Prog Neurobiol 90:285–326. Zuckerman L, Weiner I (2005): Maternal immune activation leads to behavioral and pharmacological changes in the adult offspring. J Psychiatr Res 39:311–323. Meyer U, Feldon J (2009): Neural basis of psychosis-related behaviour in the infection model of schizophrenia. Behav Brain Res 204:322–334. Meyer U, Feldon J (2009): Prenatal exposure to infection: A primary mechanism for abnormal dopaminergic development in schizophrenia. Psychopharmacology (Berl) 206:587– 602. Shi L, Fatemi SH, Sidwell RW, Patterson PH (2003): Maternal influenza infection causes marked behavioral and pharmacological changes in the offspring. J Neurosci 23:297–302. Piontkewitz Y, Arad M, Weiner I (2010): Risperidone administered during asymptomatic period of adolescence prevents the emergence of brain structural pathology and behavioral abnormalities in an animal model of schizophrenia [published online ahead of print May 3]. Schizophr Bull. 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. Zuckerman L, Weiner I (2003): Post-pubertal emergence of disrupted latent inhibition following prenatal immune activation. Psychopharmacology (Berl) 169:308 –313. Weiner I (2003): The “two-headed” latent inhibition model of schizophrenia: modeling positive and negative symptoms and their treatment. Psychopharmacology (Berl) 169:257–297. Laruelle M, Abi-Dargham A, van Dyck CH, Gil R, D’Souza CD, Erdos J, et al. (1996): Single photon emission computerized tomography imaging of amphetamine-induced dopamine release in drug-free schizophrenic subjects. Proc Natl Acad Sci U S A 93:9235–9240. Chen CC, Tung YY, Chang C (2010): A lifespan MRI evaluation of ventricular enlargement in normal aging mice [published online ahead of print February 3]. Neurobiol Aging. Malkova L, Heuer E, Saunders RC (2006): Longitudinal magnetic resonance imaging study of rhesus monkey brain development. Eur J Neurosci 24:3204 –3212. Knickmeyer RC, Styner M, Short SJ, Lubach GR, Kang C, Hamer R, et al. (2010): Maturational trajectories of cortical brain development through the pubertal transition: Unique species and sex differences in the monkey revealed through structural magnetic resonance imaging. Cereb Cortex 20:1053–1063. Lenroot RK, Giedd JN (2006): Brain development in children and adolescents: Insights from anatomical magnetic resonance imaging. Neurosci Biobehav Rev 30:718 –729.

www.sobp.org/journal

Y. Piontkewitz et al. 51. Spear LP (2000): The adolescent brain and age-related behavioral manifestations. Neurosci Biobehav Rev 24:417– 463. 52. McCormick CM, Mathews IZ (2010): Adolescent development, hypothalamic-pituitary-adrenal function, and programming of adult learning and memory. Prog Neuropsychopharmacol Biol Psychiatry 34:756 –765. 53. Brenhouse HC, Andersen SL (2011): Developmental trajectories during adolescence in males and females: A cross-species understanding of underlying brain changes [published online ahead of print May 12]. Neurosci Biobehav Rev. 54. Ming GL, Song H (2005): Adult neurogenesis in the mammalian central nervous system. Annu Rev Neurosci 28:223–250. 55. Meyer U, Nyffeler M, Engler A, Urwyler A, Schedlowski M, Knuesel I, et al. (2006): The time of prenatal immune challenge determines the specificity of inflammation-mediated brain and behavioral pathology. J Neurosci 26:4752– 4762. 56. Grecksch G, Bernstein HG, Becker A, Hollt V, Bogerts B (1999): Disruption of latent inhibition in rats with postnatal hippocampal lesions. Neuropsychopharmacology 20:525–532. 57. Tseng KY, Chambers RA, Lipska BK (2009): The neonatal ventral hippocampal lesion as a heuristic neurodevelopmental model of schizophrenia. Behav Brain Res 204:295–305. 58. Belujon P, Grace AA (2008): Critical role of the prefrontal cortex in the regulation of hippocampus-accumbens information flow. J Neurosci 28:9797–9805. 59. Lodge DJ, Grace AA (2011): Developmental pathology, dopamine, stress and schizophrenia. Int J Dev Neurosci 29:207–213. 60. Seeman MV, Lang M (1990): The role of estrogens in schizophrenia gender differences. Schizophr Bull 16:185–194. 61. Walf AA, Frye CA (2006): A review and update of mechanisms of estrogen in the hippocampus and amygdala for anxiety and depression behavior. Neuropsychopharmacology 31:1097–1111. 62. Sisk CL, Zehr JL (2005): Pubertal hormones organize the adolescent brain and behavior. Front Neuroendocrinol 26:163–174. 63. Arad M, Weiner I (2010): Contrasting effects of increased and decreased dopamine transmission on latent inhibition in ovariectomized rats and their modulation by 17beta-estradiol: An animal model of menopausal psychosis? Neuropsychopharmacology 35:1570 –1582. 64. Arad M, Weiner I (2010): Sex-dependent antipsychotic capacity of 17␤estradiol in the latent inhibition model: A typical antipsychotic drug in both sexes, atypical antipsychotic drug in males. Neuropsychopharmacology 35:2179 –2192. 65. Keshavan MS, Prasad KM, Pearlson G (2007): Are brain structural abnormalities useful as endophenotypes in schizophrenia? Int Rev Psychiatry 19:397– 406. 66. Borgwardt SJ, McGuire PK, Aston J, Gschwandtner U, Pfluger MO, Stieglitz RD, et al. (2008): Reductions in frontal, temporal and parietal volume associated with the onset of psychosis. Schizophr Res 106:108 –114. 67. Fusar-Poli P, Borgwardt S, Crescini A, D’Este G, Kempton M, Lawrie S, et al. (2010): Neuroanatomy of vulnerability to psychosis: A voxel-based meta-analysis. Neurosci Biobehav Rev 35:1175–1185. 68. Job DE, Whalley HC, Johnstone EC, Lawrie SM (2005): Grey matter changes over time in high risk subjects developing schizophrenia. Neuroimage 25:1023–1030. 69. McIntosh AM, Owens DC, Moorhead WJ, Whalley HC, Stanfield AC, Hall J, et al. (2011): Longitudinal volume reductions in people at high genetic risk of schizophrenia as they develop psychosis. Biol Psychiatry 69:953– 958. 70. Sun D, Phillips L, Velakoulis D, Yung A, McGorry PD, Wood SJ, et al. (2009): Progressive brain structural changes mapped as psychosis develops in “at risk” individuals. Schizophr Res 108:85–92. 71. Mittal VA, Daley M, Shiode MF, Bearden CE, O’Neill J, Cannon TD (2010): Striatal volumes and dyskinetic movements in youth at high-risk for psychosis. Schizophr Res 123:68 –70. 72. Stone JM, Howes OD, Egerton A, Kambeitz J, Allen P, Lythgoe DJ, et al. (2010): Altered relationship between hippocampal glutamate levels and striatal dopamine function in subjects at ultra high risk of psychosis. Biol Psychiatry 68:599 – 602. 73. Fusar-Poli P, Howes OD, Allen P, Broome M, Valli I, Asselin MC, et al. (2010): Abnormal frontostriatal interactions in people with prodromal signs of psychosis: A multimodal imaging study. Arch Gen Psychiatry 67:683– 691. 74. Lawrie SM, McIntosh AM, Hall J, Owens DG, Johnstone EC (2008): Brain structure and function changes during the development of schizophre-

Y. Piontkewitz et al. nia: The evidence from studies of subjects at increased genetic risk. Schizophr Bull 34:330 –340. 75. Ellman LM, Deicken RF, Vinogradov S, Kremen WS, Poole JH, Kern DM, et al. (2010): Structural brain alterations in schizophrenia following fetal exposure to the inflammatory cytokine interleukin-8. Schizophr Res 121: 46 –54. 76. Fatemi SH, Folsom TD (2009): The neurodevelopmental hypothesis of schizophrenia, revisited. Schizophr Bull 35:528 –548. 77. Fatemi SH, Folsom TD, Reutiman TJ, Huang H, Oishi K, Mori S (2009): Prenatal viral infection of mice at E16 causes changes in gene expression in hippocampi of the offspring. Eur Neuropsychopharmacol 19: 648 – 653.

BIOL PSYCHIATRY 2011;70:842– 851 851 78. Boksa P (2010): Effects of prenatal infection on brain development and behavior: A review of findings from animal models. Brain Behav Immun 24:881– 897. 79. Short SJ, Lubach GR, Karasin AI, Olsen CW, Styner M, Knickmeyer RC, et al. (2010): Maternal influenza infection during pregnancy impacts postnatal brain development in the rhesus monkey. Biol Psychiatry 67:965–973. 80. Li Q, Cheung C, Wei R, Hui ES, Feldon J, Meyer U, et al. (2009): Prenatal immune challenge is an environmental risk factor for brain and behavior change relevant to schizophrenia: evidence from MRI in a mouse model. PloS One 24;4:e6354. 81. Lenroot RK, Giedd JN (2010): Sex differences in the adolescent brain. Brain Cogn 72:46 –55.

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