Anxiety induced by prenatal stress is associated with suppression of hippocampal genes involved in synaptic function

Lifelong effects of prenatal and early postnatal stress on the hippocampus, amygdala, and psychological states of Holocaust survivors

This study focuses on hippocampal and amygdala volume, seed-based connectivity, and psychological traits of Holocaust survivors who experienced stress during prenatal and early postnatal development. We investigated people who lived in Central Europe during the Holocaust and who, as Jews, were in imminent danger. The group who experienced stress during their prenatal development and early postnatal (PreP) period (n = 11) were compared with a group who experienced Holocaust-related stress later in their lives: in late childhood, adolescence, and early adulthood (ChA) (n = 21). The results of volumetry analysis showed significantly lower volumes of both hippocampi and the right amygdala in the PreP group. Seed-based connectivity analysis revealed increased connectivity from the seed in the right amygdala to the middle and posterior cingulate cortex, caudate, and inferior left frontal operculum in the PreP group. Psychological testing found higher levels of traumatic stress symptoms (TCS-40) and lower levels of well-being (SOS-10) in the PreP group than in the ChA group. The results of our study demonstrate that extreme stress experienced during prenatal and early postnatal life has a profound lifelong impact on the hippocampus and amygdala and on several psychological characteristics.

Prenatal Stress and the Developing Brain: Postnatal Environments Promoting Resilience

Heightened maternal stress during pregnancy is associated with atypical brain development and an elevated risk for psychopathology in offspring. Supportive environments during early postnatal life may promote brain development and reverse atypical developmental trajectories induced by prenatal stress. We reviewed studies focused on the role of key early environmental factors in moderating associations between prenatal stress exposure and infant brain and neurocognitive outcomes. Specifically, we focused on the associations between parental caregiving quality, environmental enrichment, social support, and socioeconomic status with infant brain and neurocognitive outcomes. We examined the evidence that these factors may moderate the effects of prenatal stress on the developing brain. Complementing findings from translational models, human research suggests that high-quality early postnatal environments are associated with indices of infant neurodevelopment that have also been associated with prenatal stress, such as hippocampal volume and frontolimbic connectivity. Human studies also suggest that maternal sensitivity and higher socioeconomic status may attenuate the effects of prenatal stress on established neurocognitive and neuroendocrine mediators of risk for psychopathology, such as hypothalamic-pituitary-adrenal axis functioning. Biological pathways that may underlie the effects of positive early environments on the infant brain, including the epigenome, oxytocin, and inflammation, are also discussed. Future research in humans should examine resilience-promoting processes in relation to infant brain development using large sample sizes and longitudinal designs. The findings from this review could be incorporated into clinical models of risk and resilience during the perinatal period and used to design more effective early programs that reduce risk for psychopathology.

A comprehensive approach to modeling maternal immune activation in rodents

Prenatal brain development is a highly orchestrated process, making it a very vulnerable window to perturbations. Maternal stress and subsequent inflammation during pregnancy leads to a state referred to as, maternal immune activation (MIA). If persistent, MIA can pose as a significant risk factor for the manifestation of neurodevelopmental disorders (NDDs) such as autism spectrum disorder and schizophrenia. To further elucidate this association between MIA and NDD risk, rodent models have been used extensively across laboratories for many years. However, there are few uniform approaches for rodent MIA models which make not only comparisons between studies difficult, but some established approaches come with limitations that can affect experimental outcomes. Here, we provide researchers with a comprehensive review of common experimental variables and potential limitations that should be considered when designing an MIA study based in a rodent model. Experimental variables discussed include: innate immune stimulation using poly I:C and LPS, environmental gestational stress paradigms, rodent diet composition and sterilization, rodent strain, neonatal handling, and the inclusion of sex-specific MIA offspring analyses. We discuss how some aspects of these variables have potential to make a profound impact on MIA data interpretation and reproducibility.

Preclinical animal models of mental illnesses to translate findings from the bench to the bedside: Molecular brain mechanisms and peripheral biomarkers associated to early life stress or immune challenges

Animal models are useful preclinical tools for studying the pathogenesis of mental disorders and the effectiveness of their treatment. While it is not possible to mimic all symptoms occurring in humans, it is however possible to investigate the behavioral, physiological and neuroanatomical alterations relevant for these complex disorders in controlled conditions and in genetically homogeneous populations. Stressful and infection-related exposures represent the most employed environmental risk factors able to trigger or to unmask a psychopathological phenotype in animals. Indeed, when occurring during sensitive periods of brain maturation, including pre, postnatal life and adolescence, they can affect the offspring's neurodevelopmental trajectories, increasing the risk for mental disorders. Not all stressed or immune challenged animals, however, develop behavioral alterations and preclinical animal models can explain differences between vulnerable or resilient phenotypes. Our review focuses on different paradigms of stress (prenatal stress, maternal separation, social isolation and social defeat stress) and immune challenges (immune activation in pregnancy) and investigates the subsequent alterations in several biological and behavioral domains at different time points of animals' life. It also discusses the "double-hit" hypothesis where an initial early adverse event can prime the response to a second negative challenge. Interestingly, stress and infections early in life induce the activation of the hypothalamic-pituitary-adrenal (HPA) axis, alter the levels of neurotransmitters, neurotrophins and pro-inflammatory cytokines and affect the functions of microglia and oxidative stress. In conclusion, animal models allow shedding light on the pathophysiology of human mental illnesses and discovering novel molecular drug targets for personalized treatments.

Maternal caregiving ameliorates the consequences of prenatal maternal psychological distress on child development

Children exposed to prenatal maternal psychological distress are at elevated risk for a range of adverse outcomes; however, it remains poorly understood whether postnatal influences can ameliorate impairments related to prenatal distress. The current study evaluated if sensitivematernal care during the first postnatal year could mitigate child cognitive and emotional impairments associated with prenatal psychological distress. Prenatal maternal psychological distress was assessed via self-reports of anxiety, depression, and perceived stress for 136 mothers at five prenatal and four postpartum time points. Quality of maternal care (sensitivity to nondistress, positive regard, and intrusiveness reverse-scored) were assessed during a mother-child play interaction at 6 and 12 months. Child cognitive function and negative emotionality were assessed at 2 years, using The Bayley Scales and the Early Childhood Behavior Questionnaire. Elevated prenatal distress was associated with poorer child cognitive function and elevated negative emotionality. Children exposed to elevated prenatal maternal distress did not, however, display these outcomes if they received high-quality caregiving. Specifically, maternal care moderated the relation between prenatal psychological distress and child cognitive function and negative emotionality. This association remained after consideration of postnatal maternal psychological distress and relevant covariates. Sensitive maternal care was associated with altered offspring developmental trajectories, supporting child resilience following prenatal distress exposure.

The Behavior and Postnatal Development in Infant and Juvenile Rats After Ultrasound-Induced Chronic Prenatal Stress

Fetal development is susceptible to environmental factors. One such factor is exposure to stress during pregnancy. The present study aimed to investigate the effects of chronic prenatal stress (PS) on the development and behavior of rat offspring during infancy and juvenile ages. Existing approaches to modeling prenatal stress on animals do not correlate with the main type of stress in pregnant women, namely psychological stress. We used a new stress paradigm in the experiment, namely, stress induced by exposure to variable frequency ultrasound (US), which acted on pregnant Wistar rats on gestational days 1–21. This type of stress in rodents can be comparable to psychological stress in humans. We assessed physical development, reflex maturation, motor ability development, anxious behavior, response to social novelty, and social play behavior in male and female offspring. Additionally, we investigated maternal behavior and the effect of neonatal handling (NH) on behavior. Prenatal stress did not affect postnatal developmental characteristics in rat pups, but prenatally stressed rats had higher body weight in early and adult age than controls. Prenatal exposure to a stressor increased anxiety in the open-field test (OF), changed social preferences in the social novelty test (SN), and impaired social play behavior in males. Neonatal handling reduced anxiety and restored social behavior, but evoked hyperactive behavior in rat pups. Maternal behavior did not change. Our study demonstrated for the first time that exposure to variable frequency ultrasound during pregnancy influences offspring development and impairs behavior, correlating with the effects of other types of stress during pregnancy in rodents. This supports the idea of using this exposure to model prenatal stress.

Sex-dependent aberrant PFC development in the adolescent offspring rats exposed to variable prenatal stress

Adolescence is a remarkable period of brain development. Prenatal stress can increase the risk of various neuropsychiatric disorders. This research investigated neurochemical and behavioural changes in the offspring rats (especially adolescences) who were treated with repeated variable prenatal stress (PNS) during the third week of gestation. The study tested the concentration of brain-derived neurotrophic factor (BDNF), cluster of differentiation 68 (CD68), synaptotagmin-1(Syt-1), 5-hydroxytryptamine (5-HT), dopamine (DA), glucocorticoid receptors (GRs) and oestrogen receptors (ERs) in the PFC (prefrontal cortex). We also tested prepulse inhibition (PPI) of the acoustic startle reflex (ASR) (a measure of sensorimotor gating). The main results were as follows: PNS increased the BDNF and CD68 concentrations in adolescent females, and increased the Syt-1 concentration in adolescent males. The increases in BDNF/CD68 concentration (in females) and Syt-1/DA concentration (in males) with age were disturbed by PNS, and PNS changed the sex differences in CD68 concentration in adolescence and disturbed the sex differences in the Syt-1 concentration (in adolescence) and DA concentration (in adults). In conclusion, we found that PNS lead to Sex-dependent aberrant PFC development, and might accelerate the development of the adolescent PFC, and so that lessened the age difference (between adolescence and adulthood) and the sex difference.

Altered Hippocampal Epigenetic Regulation Underlying Reduced Cognitive Development in Response to Early Life Environmental Insults

The hippocampus is involved in learning and memory and undergoes significant growth and maturation during the neonatal period. Environmental insults during this developmental timeframe can have lasting effects on brain structure and function. This study assessed hippocampal DNA methylation and gene transcription from two independent studies reporting reduced cognitive development stemming from early life environmental insults (iron deficiency and porcine reproductive and respiratory syndrome virus (PRRSv) infection) using porcine biomedical models. In total, 420 differentially expressed genes (DEGs) were identified between the reduced cognition and control groups, including genes involved in neurodevelopment and function. Gene ontology (GO) terms enriched for DEGs were associated with immune responses, angiogenesis, and cellular development. In addition, 116 differentially methylated regions (DMRs) were identified, which overlapped 125 genes. While no GO terms were enriched for genes overlapping DMRs, many of these genes are known to be involved in neurodevelopment and function, angiogenesis, and immunity. The observed altered methylation and expression of genes involved in neurological function suggest reduced cognition in response to early life environmental insults is due to altered cholinergic signaling and calcium regulation. Finally, two DMRs overlapped with two DEGs, VWF and LRRC32, which are associated with blood brain barrier permeability and regulatory T-cell activation, respectively. These results support the role of altered hippocampal DNA methylation and gene expression in early life environmentally-induced reductions in cognitive development across independent studies.

Prenatal programming of stress responsiveness and behaviours: Progress and perspectives

Parental exposure to stress or glucocorticoids either before or during pregnancy can have profound influences on neurodevelopment, neuroendocrine function and behaviours in offspring. Specific outcomes are dependent on the nature, intensity and timing of the exposure, as well as species, sex and age of the subject. Most recently, it has become evident that outcomes are not confined to first-generation offspring and that there may be intergenerational and transgenerational transmission of effects. There has been intense focus on the mechanisms by which such early exposure leads to long-term and potential transgenerational outcomes, and there is strong emerging evidence that epigenetic processes (histone modifications, DNA methylation, and small non-coding RNAs) are involved. New knowledge in this area may allow the development of interventions that can prevent, ameliorate or reverse the long-term negative outcomes associated with exposure to early adversity. This review will focus on the latest research, bridging human and pre-clinical studies, and will highlight some of the limitations, challenges and gaps that exist in the field.

H3K9 Acetylation of Tph2 Involved in Depression-like Behavior in Male, but not Female, Juvenile Offspring Rat Induced by Prenatal Stress

Increasing evidence has shown that prenatal stress (PS) could cause depression-like behavior in the offspring, which is sex-specific. However, the underlying mechanisms remain to be elucidated. This study is to investigate the involvement of tryptophan hydroxylase 2 (Tph2) H3K9 acetylation (H3K9ac) modification on PS-induced depression-like behavior in juvenile offspring rats (JOR). PS models were established, with or without trichostatin A (TSA) treatment. Animal behavior was assessed by the sucrose preference test (SPT) and forced swimming test (FST). The mRNA and protein expression levels of TPH2 in the dorsal raphenucleus (DRN), hippocampus, and prefrontal cortex were detected with quantitative real-time PCR and Western blot analysis, respectively. The Tph2 H3K9ac levels in the hippocampus were also analyzed. SPT and FST showed significantly reduced sucrose preference and significantly prolonged immobility in PS-induced male juvenile offspring rats (MJOR). Moreover, the mRNA and protein expression levels of TPH2 in the DRN and hippocampus were significantly declined, while the hippocampal Tph2 H3K9ac levels were significantly declined in the PS-induced MJOR. Furthermore, the PS-induced effects in MJOR could be reversed by the microinjection of TSA. However, no significant effects were observed for the female juvenile offspring rats (FJORs). In conclusion, our results showed that the Tph2 H3K9ac modification is only involved in PS-induced depression-like behavior in MJOR, in a sex-specific manner. These findings might contribute to the understanding of the disease pathogenesis and clinical treatment in future.

Influence of early stress on memory reconsolidation: Implications for post-traumatic stress disorder treatment

Post-traumatic stress disorder (PTSD) is a common consequence of exposure to a life-threatening event. Currently, pharmacological treatments are limited by high rates of relapse, and novel treatment approaches are needed. We have recently demonstrated that propranolol, a β-adrenergic antagonist, inhibited aversive memory reconsolidation in animals. Following this, in an open-label study 70% of patients with PTSD treated with propranolol during reactivation of traumatic memory exhibited full remission. However, the reason why 30% of these patients did not respond positively to propranolol treatment is still unclear. One of the major candidates as factor of treatment resistance is the patient's early-life traumatic history. To test the role of this factor, mice with pre- or postnatal stress are being tested in fear conditioning and in a new behavioral task, the "city-like", specifically designed as a mouse model of PTSD. After reactivation of the traumatic event, mice received propranolol injection to block the noradrenergic system during memory reconsolidation. Results show that, in the “city-like” test, control mice strongly avoided the shock compartment but also the compartments containing cues associated with the electric shocks. Injection of propranolol after reactivation greatly reduced the memory of the traumatic event, but this effect was not present when mice had received pre- or postnatal stress. Moreover, propranolol produced only a very weak effect in the fear conditioning test, and never changed the corticosterone level whatever the behavioral experiment. Taken together our results suggest that our new behavioural paradigm is well adapted to PTSD study in mice, and that early stress exposure may have an impact on propranolol PTSD treatment outcome. These data are critical to understanding the effect of propranolol treatment, in order to improve the therapeutic protocol currently used in humans.

Impact of neonatal iron deficiency on hippocampal DNA methylation and gene transcription in a porcine biomedical model of cognitive development

BACKGROUND

Iron deficiency is a common childhood micronutrient deficiency that results in altered hippocampal function and cognitive disorders. However, little is known about the mechanisms through which neonatal iron deficiency results in long lasting alterations in hippocampal gene expression and function. DNA methylation is an epigenetic mark involved in gene regulation and altered by environmental factors. In this study, hippocampal DNA methylation and gene expression were assessed via reduced representation bisulfite sequencing and RNA-seq on samples from a previous study reporting reduced hippocampal-based learning and memory in a porcine biomedical model of neonatal iron deficiency.

RESULTS

In total 192 differentially expressed genes (DEGs) were identified between the iron deficient and control groups. GO term and pathway enrichment analysis identified DEGs associated with hypoxia, angiogenesis, increased blood brain barrier (BBB) permeability, and altered neurodevelopment and function. Of particular interest are genes previously implicated in cognitive deficits and behavioral disorders in humans and mice, including HTR2A, HTR2C, PAK3, PRSS12, and NETO1. Altered genome-wide DNA methylation was observed across 0.5 million CpG and 2.4 million non-CpG sites. In total 853 differentially methylated (DM) CpG and 99 DM non-CpG sites were identified between groups. Samples clustered by group when comparing DM non-CpG sites, suggesting high conservation of non-CpG methylation in response to neonatal environment. In total 12 DM sites were associated with 9 DEGs, including genes involved in angiogenesis, neurodevelopment, and neuronal function.

CONCLUSIONS

Neonatal iron deficiency leads to altered hippocampal DNA methylation and gene regulation involved in hypoxia, angiogenesis, increased BBB permeability, and altered neurodevelopment and function. Together, these results provide new insights into the mechanisms through which neonatal iron deficiency results in long lasting reductions in cognitive development in humans.

Stress during the gestational period modifies pups' emotionality parameters and favors preference for morphine in adolescent rats

Experimental animal studies have shown that early life periods are highly vulnerable to environmental factors, which may exert prolonged impact on HPA axis function and on subsequent neurochemical and behavioral responses in adulthood. Here we evaluated the influence of environmental stressful situations in two different early life stages on stress-related behaviors, and morphine-conditioned place preference (CPP), which is indicative of addiction. While in the gestational stress (Gest-S) dams were exposed to daily sessions of chronic mild stress (CMS) for 2 weeks, in the postnatal stress (post-NS) the offspring were exposed daily to neonatal isolation from postnatal day (PND) 2 to PND 9 for 60 min. Animals exposed to post-NS showed lesser anxiety in different behavioral paradigms (elevated plus maze-EPM and defensive burying test-DBT) as well as increased exploratory behavior (open-field task-OFT), and no preference for morphine in CPP. In contrast, animals exposed to Gest-S showed increased corticosterone plasma levels together with anxiety symptoms and greater preference for morphine following three days of drug withdrawal. Our findings indicate that the gestational period is critical for stress, whose effects may be manifest throughout life. On the other hand, post-NS can trigger neuroadaptations able to overcome emotional consequences of early life. We hypothesized that Gest-S is able to modify responses to opioids along adulthood, which may facilitate development of addiction to these drugs.

Effects of prenatal stress and neonatal handling on anxiety, spatial learning and serotonergic system of male offspring mice

Environmental factors during perinatal period have various effects on behavior. The present study examined the effects of prenatal stress and neonatal handling on anxiety and spatial learning of offspring. Prenatal stress increased anxiety-related behavior of adult offspring, whereas neonatal handling had no effect. In contrast, spatial learning was not affected by prenatal stress, but improved by neonatal handling in both prenatally stressed and non-stressed mice. Next, to elucidate possible brain mechanisms mediating effects of environmental factors on behavior, we focused on serotonin (5-HT) system in the frontal cortex and hippocampus which is involved in anxiety and learning. We examined effects of environmental factors on the mRNA expression of 5-HT1A, 5-HT2A and 5-HT2C receptors in the frontal cortex and hippocampus during postnatal period and adulthood. Both prenatal stress and neonatal handling altered the mRNA expression of 5-HT receptors. These effects were dependent on environmental factors, brain regions and developmental stages. In summary, the present study revealed that prenatal stress and neonatal handling had differential effects on anxiety and spatial learning of offspring, and concomitantly the expression of 5-HT receptors. It was also shown that the effects of prenatal stress on 5-HT system were recovered partially by neonatal handling.

Fetal sex modifies effects of prenatal stress exposure and adverse birth outcomes

Prenatal maternal stress is associated with pregnancy complications, poor fetal development and poor birth outcomes. Fetal sex has also been shown to affect the course of pregnancy and its outcomes. The aim of this study was to evaluate whether fetal sex modifies the association between continuous exposure to life-threatening rocket attack alarms and adverse pregnancy outcomes. A retrospective cohort study was conducted in which the exposed group was comprised of 1846 women exposed to rocket-attack alarms before and during pregnancy. The unexposed group, with similar sociodemographic characteristics, delivered during the same period of time at the same medical center, but resided out of rocket-attack range. Multivariable models for each gender separately, controlling for possible confounders, evaluated the risk associated with exposure for preterm births (PTB), low birthweight (LBW), small for gestational age and small head circumference (HC). In both univariable and multivariable analyses exposure status was a significant risk factor in female fetuses only: PTB (adj. OR = 1.43; 1.04-1.96), LBW (adj. OR = 1.41; 1.02-1.95) and HC < 31 cm (adj. OR = 1.78; 1.11-2.88). In addition, regarding all adverse outcomes, the male-to-female ratio was higher in the exposed group than in the unexposed group. The findings support the hypothesis that male and female fetuses respond differentially to chronic maternal stress.

Neonatal handling: an overview of the positive and negative effects

As one of the first rodent models designed to investigate the effects of early-life experiences, the neonatal handling paradigm has helped us better understand how subtle changes in the infant environment can powerfully drive neurodevelopment of the immature brain in typical or atypical trajectories. Here, we review data from more than 50 years demonstrating the compelling effects of neonatal handling on behavior, physiology, and neural function across the lifespan. Moreover, we present data that challenge the classical view of neonatal handling as an animal model that results only in positive/beneficial outcomes. Indeed, the overall goal of this review is to offer the suggestion that the effects of early-life experiences-including neonatal handling-are nuanced rather than unidirectional. Both beneficial and negative outcomes may occur, depending on the parameters of testing, sex of the subject, and neurobehavioral system analyzed.

Glucocorticoids and fetal programming part 1: Outcomes

Fetal development is a critical period for shaping the lifelong health of an individual. However, the fetus is susceptible to internal and external stimuli that can lead to adverse long-term health consequences. Glucocorticoids are an important developmental switch, driving changes in gene regulation that are necessary for normal growth and maturation. The fetal hypothalamic-pituitary-adrenal (HPA) axis is particularly susceptible to long-term programming by glucocorticoids; these effects can persist throughout the life of an organism. Dysfunction of the HPA axis as a result of fetal programming has been associated with impaired brain growth, altered behaviour and increased susceptibility to chronic disease (such as metabolic and cardiovascular disease). Moreover, the effects of glucocorticoid-mediated programming are evident in subsequent generations, and transmission of these changes can occur through both maternal and paternal lineages.

Effects of constant light during perinatal periods on the behavioral and neuronal development of mice with or without dietary lutein

Constant light conditions (LL) carry a risk of disrupting the biological clock of developing animals. Our purpose in this study was to investigate what disorders occur in animals receiving an LL stress during the late embryonic and suckling periods as compared with animals housed in dark-light (14 h-10 h) conditions (DL). In addition, we examined ameliorating effects against the disorder by the oral administration of lutein as an antioxidant. LL caused hypertrophy of the spleen and induced a higher expression of serotonin transporter (5HTT) in the corpus striatum and hippocampus in 15-day-old pups. In 9-week-old offspring, LL caused abnormal behavior in the elevated plus-maze test. The expression levels of 5HTT in the brain of the LL group changed to lower than those in DL group. The oral administration of lutein lessened the abnormality in behavior and 5HTT expression in the hippocampus to a certain degree although the expression levels of 5HTT in the corpus striatum were not altered by lutein diet. LL also induced disorders in the maternal brain with lower expression levels of 5HTT and neuregulin 1. These results indicate that LL during the perinatal periods may induce some neuronal abnormalities in both offspring and mothers that may be partially ameliorated by dietary lutein as an antioxidant.

Early-life stress impacts the developing hippocampus and primes seizure occurrence: cellular, molecular, and epigenetic mechanisms

Early-life stress includes prenatal, postnatal, and adolescence stress. Early-life stress can affect the development of the hypothalamic-pituitary-adrenal (HPA) axis, and cause cellular and molecular changes in the developing hippocampus that can result in neurobehavioral changes later in life. Epidemiological data implicate stress as a cause of seizures in both children and adults. Emerging evidence indicates that both prenatal and postnatal stress can prime the developing brain for seizures and an increase in epileptogenesis. This article reviews the cellular and molecular changes encountered during prenatal and postnatal stress, and assesses the possible link between these changes and increases in seizure occurrence and epileptogenesis in the developing hippocampus. In addititon, the priming effect of prenatal and postnatal stress for seizures and epileptogenesis is discussed. Finally, the roles of epigenetic modifications in hippocampus and HPA axis programming, early-life stress, and epilepsy are discussed.

Prenatal stress changes the glycoprotein GPM6A gene expression and induces epigenetic changes in rat offspring brain

Prenatal stress (PS) exerts strong impact on fetal brain development and on adult offspring brain functions. Previous work demonstrated that chronic stress alters the mRNA expression of GPM6A, a neuronal glycoprotein involved in filopodium extension. In this work, we analyzed the effect of PS on gpm6a expression and the epigenetic mechanisms involved. Pregnant Wistar rats received restraint stress during the last week of gestation. Male offspring were sacrificed on postnatal days 28 and 60. Hippocampus and prefrontal cortex samples were analyzed for gene expression (qPCR for mRNAs and microRNAs), methylation status (bisulfite conversion) and protein levels. Hippocampal neurons in culture were used to analyze microRNA overexpression effects. Prenatal stress induced changes in gpm6a levels in both tissues and at both ages analyzed, indicating a persistent effect. Two CpG islands in the gpm6a gene were identified. Variations in the methylation pattern at three specific CpGs were found in hippocampus, but not in PFC samples from PS offspring. microRNAs predicted to target gpm6a were identified in silico. qPCR measurements showed that PS modified the expression of several microRNAs in both tissues, being microRNA-133b the most significantly altered. Further studies overexpressing this microRNA in neuronal cultures showed a reduction in gmp6a mRNA and protein level. Moreover filopodium density was also reduced, suggesting that GPM6A function was affected. Gestational stress affected gpm6a gene expression in offspring likely through changes in methylation status and in posttranscriptional regulation by microRNAs. Thus, our findings propose gpm6a as a novel target for epigenetic regulation during prenatal stress.

Prenatal stress alters noradrenergic modulation of LTP in hippocampal slices

Long-term effects of stress during pregnancy on brain and behavior have been analyzed extensively in recent years. These effects include changes in emotional behavior, a reduction in learning capacity, and ability to generate long-term potentiation (LTP) in the offspring. In earlier studies, we and others have described a difference in ability to express LTP in dorsal and ventral sectors of the hippocampus (DH and VH, respectively) and its modification by prior stress. We now found that norepinephrine (NE) facilitated conversion of short-term potentiation to LTP in the normal DH but not in VH. Prenatal stress (PS) switched the locus of the facilitating action of NE from the DH to the VH. The effects of NE are likely to be mediated by activation of calcium stores. PS also facilitated ( S)-3,5-dihydroxyphenylglycine hydrate (DHPG)-induced LTD in the VH, assumed to be mediated by release of calcium from stores. These observations have important implications for the role of the hippocampus in cognitive and emotional memories.

Early adverse experience alters dendritic spine density and gene expression in prefrontal cortex and hippocampus in lambs

In the laboratory, prenatal stress produces alterations in the structure and function of corticolimbic neurons. Here we report changes in gene expression and corticolimbic dendritic spine morphology in the offspring of pregnant ewes subjected to aversive interactions with human handlers during the last five weeks of pregnancy (AVS) compared to control dams that received gentle handling (GEN). AVS lambs had higher spine density on pyramidal neurons in area CA1 of the hippocampus and in medial prefrontal cortex compared to GEN lambs, as well as a lower ratio of mushroom spines to stubby and thin spines in area CA1. Expression of genes involved in brain development and spine morphogenesis was decreased in hippocampus and prefrontal cortex in AVS compared to GEN lambs. This study is the first demonstration that an ecologically relevant aversive experience in a field setting alters neuronal structure similarly to previous reports from laboratory settings and that even for animals domesticated over 12,000 years ago, an apparently mild stressor, resulting from human-animal interactions, can have similarly profound impacts on corticolimbic morphology.

Prenatal stress affects network properties of rat hippocampal neurons

BACKGROUND

Long-term effects of stress during pregnancy on brain and behavior have been analyzed extensively in recent years. One major problem with these studies is the inability to separate between the net effects of the prenatal stress (PS) and the effects of the stressed mother and siblings on the newborn animals.

METHODS

To address these issues, we studied morphological and electrophysiological properties of neurons in dissociated cultures of the hippocampus taken from newborn PS rats. We complemented these studies with experiments on behaving rats and recordings from slices taken from PS rats and their control rats.

RESULTS

While the density of cultured neurons was not different between PS and control rats, there were fewer glutamic acid decarboxylase-positive neurons in the former cultures. Additionally, cells taken from PS pups developed more extensive dendrites than control animals. These differences were correlated with a higher rate of synchronous activity in the PS cultures and a lower rate of spontaneous miniature inhibitory postsynaptic current activity. There were no differences in the excitatory synaptic currents or the passive and active properties of the recorded neurons in the two groups. Young PS rats were more motile in open field and elevated plus maze than control rats, and they learned faster to navigate in a water maze. Slices taken from hippocampus of PS rats expressed less paired-pulse inhibition than slices from control rats.

CONCLUSIONS

These results indicate that PS affects network properties of hippocampal neurons, by reducing gamma-aminobutyric acidergic inhibition.

Involvement of pGluR1, EAAT2 and EAAT3 in offspring depression induced by prenatal stress

It is widely known that prenatal stress (PS) exposure causes depression-like behaviour to offspring, as well as maladaptive responses including neurobiological and physiological changes. However, the underlying mechanism of PS induced juvenile-onset depression remains largely unravelled. The inadequacies of monoamine deficiency hypothesis, the emerging evidence of altered glutamate neurotransmission in mood disorders, as well as our previous studies inspired us to assess the potential role of glutamatergic system in the pathogenesis of juvenile depression. In this research, we examined the expression of phosphorylated GluR1 subunit of ionotropic receptor alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), the Na+-dependent glutamate transporters excitatory amino acid transporter 2 (EAAT2) and EAAT3 in the hippocampus, striatum and frontal cortex of 1-month-old rat offspring after mid and late PS exposure. Prenatally stressed offspring rats showed significantly prolonged duration of immobility and shortened immobility latency in tail suspension test. We also detected that PS significantly altered the expression of glutamate receptor and glutamate transporters of these depressed rats. In brief, the changes of phosphorylated GluR1 subunit of AMPAR protein level in the hippocampus and frontal cortex, as well as markedly decreased EAAT2 mRNA expression in the hippocampus, striatum and frontal cortex and EAAT3 mRNA expression in the hippocampus of stressed rats were both observed. These results underpinned that glutamate receptors and glutamate transporters might be involved in the progress of depression-like behaviour in juvenile rat offspring induced by PS.

Low dose prenatal ethanol exposure induces anxiety-like behaviour and alters dendritic morphology in the basolateral amygdala of rat offspring

Prenatal exposure to high levels of alcohol is strongly associated with poor cognitive outcomes particularly in relation to learning and memory. It is also becoming more evident that anxiety disorders and anxiety-like behaviour can be associated with prenatal alcohol exposure. This study used a rat model to determine if prenatal exposure to a relatively small amount of alcohol would result in anxiety-like behaviour and to determine if this was associated with morphological changes in the basolateral amygdala. Pregnant Sprague Dawley rats were fed a liquid diet containing either no alcohol (Control) or 6% (vol/vol) ethanol (EtOH) throughout gestation. Male and Female offspring underwent behavioural testing at 8 months (Adult) or 15 months (Aged) of age. Rats were perfusion fixed and brains were collected at the end of behavioural testing for morphological analysis of pyramidal neuron number and dendritic morphology within the basolateral amygdala. EtOH exposed offspring displayed anxiety-like behaviour in the elevated plus maze, holeboard and emergence tests. Although sexually dimorphic behaviour was apparent, sex did not impact anxiety-like behaviour induced by prenatal alcohol exposure. This increase in anxiety – like behaviour could not be attributed to a change in pyramidal cell number within the BLA but rather was associated with an increase in dendritic spines along the apical dendrite which is indicative of an increase in synaptic connectivity and activity within these neurons. This study is the first to link increases in anxiety like behaviour to structural changes within the basolateral amygdala in a model of prenatal ethanol exposure. In addition, this study has shown that exposure to even a relatively small amount of alcohol during development leads to long term alterations in anxiety-like behaviour.

Environmental Enrichment during Gestation Improves Behavior Consequences and Synaptic Plasticity in Hippocampus of Prenatal-Stressed Offspring Rats

Prenatal stress can result in various behavior deficits in offspring. Here we tested the effects of environmental enrichment during gestation used as a preventive strategy on the behavior deficits of prenatal-stressed offspring rats as well as the underlying structure basis. We compared the effect size of environmental enrichment during gestation on prenatal-stressed offspring to that of environmental enrichment after weaning. Our results showed that environmental enrichment during gestation partially prevented anxiety and the damage in learning and memory in prenatal-stressed offspring as evaluated by elevated plus-maze test and Morris water maze test. At the same time, environmental enrichment during gestation inhibited the decrease in spine density of CA1 and dentate gyrus neurons and preserved the expression of synaptophysin and glucocorticoid receptors (GRs) in the hippocampus of prenatal-stressed offspring. There was no significant difference in offspring behavior between 7-day environmental enrichment during gestation and 14-day offspring environmental enrichment after weaning. These data suggest that environmental enrichment during gestation effectively prevented the behavior deficits and the abnormal synapse structures in prenatal-stressed offspring, and that it can be used as an efficient preventive strategy against prenatal stresses.

Synchronized spike waves in immature dentate gyrus networks

At early developmental stages, immature neuronal networks of the neocortex and hippocampus spontaneously exhibit synchronously oscillating activities, which are believed to play roles in normal circuit maturation. The tissue development of the dentate gyrus (DG) in the hippocampal formation is exceptionally late compared with other brain regions and persists until postnatal periods. Using patch-clamp recording and functional multineuron calcium imaging, we found that the DG networks of postnatal day (P)3-7 mice spontaneously generated traveling waves of action potentials, which were initiated at the upper blade of the granule cell layer and propagated to the lower blade. The propagation was dependent on glutamatergic and electrical synapses, but not on GABAergic receptor activity. Remarkably, the DG waves were almost completely abolished in offspring born to female rats exposed to restraint stress during pregnancy. In the prenatally stressed offspring, DG granule cell dendrites developed normally until P3 and showed atrophy by P9. Thus, the DG waves may be required for the maturation of DG granule cells.

The influence of chronic stress imposed on pregnant rats on the induced bone loss in their adult offspring

BACKGROUND AND OBJECTIVE

Stress during pregnancy may alter offspring susceptibility to diseases during adulthood. In the present study, female Lewis rats were subjected to chronic stress during the gestational period, and the effect of this stress was evaluated histometrically on the progression of ligature-induced bone loss in their adult offspring.

MATERIAL AND METHODS

After confirming pregnancy, half of the pregnant rats were randomly designated as control animals (no stress regimen was imposed), and the other half was submitted to a chronic stress model (immobilization at cold temperature) between the 7th and the 18th gestational day. After birth, 12 male rats delivered by stressed mothers - Group 1 (G1) - and 12 male rats delivered by non-stressed mothers - Group 2 (G2) - were selected. When birthed rats reached 250 g of body weight, a silk ligature was placed around their maxillary right second molar in order to induce bone loss. The non-ligated left side served as a control. Sixty days later, these animals were sacrificed by anaesthetic overdose. After routine laboratorial processing, images of the histological sections were digitized and submitted for histometric measurement using two parameters: histological attachment loss and bone loss.

RESULTS

On the ligated side, G1 presented with greater histological attachment and bone loss than G2 (p<0.05). On the non-ligated control side, neither of the groups presented with alterations in these parameters (p>0.05).

CONCLUSION

The chronic stress regimen imposed on pregnant rats produced a greater progression of ligature-induced bone loss in their adult offspring.

Hyperthermia protects mice against chronic unpredictable stress-induced anxiety-like behaviour and hippocampal CA3 cell apoptosis

PURPOSE

It is widely accepted that chronic stress can induce anxiety; however, the cellular and molecular mechanisms of stress-induced anxiety are far from being elucidated. Hyperthermia has been shown to induce expression of heat shock proteins (HSPs) to provide protection against a variety of stresses. To our knowledge, the effect of hyperthermia on the development of chronic unpredictable stress (CUS)-induced anxiety has not been studied. This study was to determine the relationship between hyperthermia induced Hsp72 and CUS related anxiety.

MATERIALS AND METHODS

Heat shock factor 1 knockout (hsf1(-/-)) and wild-type (hsf1(+/+)) mice were subjected to CUS with or without hyperthermia treatment. Anxiety-like behaviours were evaluated by elevated plus maze and open field tests. Apoptosis in the hippocampal CA3 area was detected by TUNEL staining. Hsp72 protein level in the hippocampus was measured by Western blot.

RESULTS

CUS caused significant apoptosis in hippocampal CA3 cells in both hsf1(-/-) and hsf1(+/+) mice, which significantly correlated with anxiety-like behaviours. Hyperthermia induced Hsp72 expression in hsf1(+/+) mice, but not in hsf1(-/-) mice. Importantly, hyperthermia protected hsf1(+/+) mice against developing CUS-related anxiety-like behaviours and reduced CUS-induced apoptosis in hippocampal CA3 cells. In contrast, hyperthermia exhibited no protective role in hsf1(-/-) mice.

CONCLUSIONS

Apoptosis of hippocampal CA3 cells is involved in the development of anxiety-like behaviours underlying CUS. Hsp72 protein is a crucial player in the protective effect of hyperthermia against CUS-induced apoptosis and development of anxiety-like behaviours. Our study suggests hyperthermia is an effective treatment for CUS-induced mood disorders.

Sex-dependent changes induced by prenatal stress in cortical and hippocampal morphology and behaviour in rats: an update

Recent prospective studies have shown that gestational stress in humans is more likely to cause cognitive and emotional problems in the offspring if it occurs during weeks 12-20 of pregnancy. There are also suggestions that such problems may be gender dependent. This review describes recent studies that found sex differences in the behaviour and brain morphology of rats stressed prenatally during the equivalent period of neuronal development in humans. Learning deficits are more prevalent in males and anxious behaviour in females but their appearance depends also on the timing and intensity of the stress and the age when the offspring were tested. Cognitive deficits and anxiety are linked to a sex-dependent reduction in neurogenesis and in measures of dendritic morphology in the prefrontal cortex and hippocampal formation. Maternal adrenalectomy prior to the stress prevents the anxiety in both sexes and learning deficits in males. Corticosterone administration to the dam to mimic levels induced by stress reinstates only the anxiety, indicating that it arises from foetal exposure to corticosterone from the maternal circulation. Learning deficits in males may result from a combination of a reduction in testosterone and in aromatase activity, together with the action of other adrenal hormones.

Effects of stress across the lifespan

Stress is a known precipitant for metabolic and neurological diseases, with sensitive periods identified across the developmental continuum from conception to old age. However, the effects of stress may vary depending on the point or points along the developmental trajectory when adversity strikes. Past research has emphasized the consequences of stress on fully developed physiological systems in the brain and periphery, but more recent studies have explored the impact of stress on systems at different stages of maturation, with differential effects being revealed. This review provides an overview of the diverse effects of stress at critical developmental stages and the potential outcomes that may be associated with experiencing environmental adversity during ontogeny.

Prenatal stress and neonatal handling induce sex-specific changes in dendritic complexity and dendritic spine density in hippocampal subregions of prepubertal rats

Maternal stress during gestation in humans and experimental animals can result in emotional and cognitive dysfunction in the offspring. To facilitate our understanding of the underlying neuronal changes induced by prenatal stress (PNS), the dendritic and synaptic development was analyzed in three-dimensionally reconstructed Golgi-impregnated neurons in the hippocampal formation of offspring from pregnant dams which were stressed from day 15-20 by varied stressors. The analysis was focused on prepubertal rats and on the comparison of stress vulnerabilities in male and female offspring. In the hippocampal CA1 region PNS increased spine density on pyramidal neurons only in males, which thereby reached the levels observed in control females. On granular neurons of the dentate gyrus, PNS altered spine-density, dendritic length and dendritic complexity in opposite directions in males and females. In the CA3 area, PNS resulted in shorter and less complex dendrites in both sexes compared with unstressed controls. Another aim was to assess whether neonatal environmental interventions, such as handling (H) during the first 10 postnatal days, can reverse PNS-induced neuronal changes. We show here for the first time that H can "reverse" or prevent PNS-induced changes in spine density and dendritic length and complexity in a sex-, region- and dendrite-specific manner. These findings indicate that the sex-specific changes of neuronal and synaptic features in the hippocampal formation may represent a neuronal substrate of the stress-induced behavioral alterations and that these changes can be partly "normalized" by neonatal interventions.

Differential effect of prenatal stress on the expression of corticotrophin-releasing hormone and its receptors in the hypothalamus and amygdala in male and female rats

The present study examined the effect of prenatal stress in rats from days 13-20 of gestation on anxiogenic behaviour in the elevated plus maze (EPM) together with changes in the gene expression of corticotrophin-releasing hormone (CRH), its receptors, CRHR1 and CRHR2, as well as CRH binding protein (CRH-BP) in the paraventricular nucleus (PVN) and amygdala of their male and female offspring. Both prenatally-stressed (PS) males and females showed heightened anxiety in the EPM. Prenatal stress did not alter the gene expression of CRH or its receptors in the male PVN, although it decreased CRH-BP mRNA, which could augment the activity of free CRH. In the PVN of PS females, there was an increase in the expression of CRH, coupled with a decrease in that of CRHR2 and CRH-BP. These changes are compatible with the greater activation of the hypothalamic pituitary adrenal axis to stress in females. Anxiogenic behaviour of PS rats was associated with a reduction of CRHR2 mRNA and of CRH-BP mRNA in the amygdala of males and an increase in CRH mRNA and decrease in CRHR2 mRNA in females. Two hours after acute stress of exposure to the elevated plus maze in which heightened anxiety was manifested, increases were seen only in the amygdala of females in CRH and CRHR1 signalling, whereas CRHR2 mRNA was reduced in both sexes. The data show that both prenatal stress and acute stress in adulthood have a differential sex-dependent effect on the expression of CRH its receptors and binding protein in the PVN and amygdala of rats.

Strain dependent effects of prenatal stress on gene expression in the rat hippocampus

Multiple animal models have been developed to recapitulate phenotypes of the human disease, schizophrenia. A model that simulates many of the cognitive and sensory deficits of the disorder is the use of random variable prenatal stress (PS) in the rat. These deficits suggest a molecular origin in the hippocampus, a brain region that plays a role in the regulation of stress. To study both hippocampal gene expression changes in offspring of prenatally stressed dams and to address genetic variability, we used a random array of prenatal stressors in three different rat strains with diverse responses to stress: Fischer, Sprague-Dawley, and Lewis rats. Candidate genes involved in stress, schizophrenia, cognition, neurotrophic effects, and immunity were selected for assessment by real-time quantitative PCR under resting conditions and following a brief exposure to restraint stress. PS resulted in significant differences in gene expression in the offspring that were strain dependent. mRNA expression for the N-methyl-D-aspartate receptor subtype 2B (Grin2b) was increased, and tumor necrosis factor-alpha (Tnfα) transcript was decreased in PS Sprague-Dawley and Lewis rats, but not in the Fischer rats. Expression of brain-derived neurotrophic factor (Bdnf) mRNA in the hippocampus was increased after an acute stress in all controls of each strain, yet a decrease was seen after acute stress in the PS Sprague-Dawley and Lewis rats. Expression of the glucocorticoid receptor (Nr3c1) was decreased in the Fischer strain when compared to Lewis or Sprague-Dawley rats, though the Fischer rats had markedly higher α7 nicotinic receptor (Chrna7) expression. The expression differences seen in these animals may be important elements of the phenotypic differences seen due to PS and genetic background.

Role of maternal 5-HT(1A) receptor in programming offspring emotional and physical development

Serotonin(1A) receptor (5-HT(1A)R) deficiency has been associated with anxiety and depression and mice with genetic receptor inactivation exhibit heightened anxiety. We have reported that 5-HT(1A)R is not only a genetic but also a maternal 'environmental' factor in the development of anxiety in Swiss-Webster mice. Here, we tested whether the emergence of maternal genotype-dependent adult anxiety is preceded by early behavioral abnormalities or whether it is manifested following a normal emotional development. Pups born to null or heterozygote mothers had significantly reduced ultrasonic vocalization (USV) between postnatal day (P) 4 and 12, indicating an influence of the maternal genotype. The offspring's own genotype had an effect limited to P4. Furthermore, we observed reduced weight gain in the null offspring of null but not heterozygote mothers, indicating that a complete maternal receptor deficiency compromises physical development of the offspring. Except a short perinatal deficit during the dark period, heterozygote females displayed normal maternal behavior, which, with the early appearance of USV deficit, suggests a role for 5-HT(1A)R during pre-/perinatal development. Consistent with this notion, adult anxiety in the offspring is determined during the pre-/perinatal period. In contrast to heterozygote females, null mothers exhibited impaired pup retrieval and nest building that may explain the reduced weight gain of their offspring. Taken together, our data indicate an important role for the maternal 5-HT(1A)R in regulating emotional and physical development of their offspring. Because reduced receptor binding has been reported in depression, including postpartum depression, reduced 5-HT(1A)R function in mothers may influence the emotional development of their offspring.

Prenatal stress: role in psychotic and depressive diseases

RATIONALE

The birth of neurons, their migration to appropriate positions in the brain, and their establishment of the proper synaptic contacts happen predominately during the prenatal period. Environmental stressors during gestation can exert a major impact on brain development and thereby contribute to the pathogenesis of neuropsychiatric illnesses, such as depression and psychotic disorders including schizophrenia.

OBJECTIVE

The objectives here are to present recent preclinical studies of the impact of prenatal exposure to gestational stressors on the developing fetal brain and discuss their relevance to the neurobiological basis of mental illness. The focus is on maternal immune activation, psychological stresses, and malnutrition, due to the abundant clinical literature supporting their role in the etiology of neuropsychiatric illnesses.

RESULTS

Prenatal maternal immune activation, viral infection, unpredictable psychological stress, and malnutrition all appear to foster the development of behavioral abnormalities in exposed offspring that may be relevant to the symptom domains of schizophrenia and psychosis, including sensorimotor gating, information processing, cognition, social function, and subcortical hyperdopaminergia. Depression-related phenotypes, such as learned helplessness or anxiety, are also observed in some model systems. These changes appear to be mediated by the presence of proinflammatory cytokines and/or corticosteroids in the fetal compartment that alter the development the neuroanatomical substrates involved in these behaviors.

CONCLUSION

Prenatal exposure to environmental stressors alters the trajectory of brain development and can be used to generate animal preparations that may be informative in understanding the pathophysiological processes involved in several human neuropsychiatric disorders.

Sex-specificity in transgenerational epigenetic programming

Prenatal programming of the epigenome is a critical determinant in offspring outcome and stands at the interface between environment and genetics. Maternal experiences such as stress and obesity are associated with a host of neurodevelopmental and metabolic diseases, some of which have been characterized into the second and third generations. The mechanism through which determinants such as maternal diet or stress contribute to disease development likely involves a complex interaction between the maternal environment, placental changes, and epigenetic programming of the embryo. While we have begun to more fully appreciate and explore the epigenome in determination of disease risk, we know little as to the contribution embryo sex makes in epigenetic regulation. This review discusses the importance of sex differences in the transmission and inheritance of traits that are generated in the prenatal environment using models of maternal stress and diet.

Maternal stress induces long-lasting Purkinje cell developmental impairments in mouse offspring

A number of clinical studies suggest that prenatal stress can be a risk factor in the development of various psychopathologies, including schizophrenia, depression, anxiety, and autism. The cerebellar vermis has been shown to be involved in most of these disorders. In the present study, therefore, we evaluate the effect of maternal stress on long-term alterations in vermal Purkinje cell morphology. Furthermore, to discern whether these structural changes are associated with anxious behavior, the exploratory drive in the elevated plus maze was evaluated. Pregnant CF-1 mice were randomly assigned to control (n = 14) or stressed (n = 16) groups. Dams of the stressed group were subjected to restraint stress between gestational days 14 and 20, while control pregnant dams remained undisturbed in their home cages. Anxious behavior and Purkinje cell morphology were evaluated in three ontogenetic stages: postweaning, adolescence, and adulthood. Although exploratory behavior in the elevated plus maze was unaffected by prenatal stress, the Purkinje cell morphology showed a transient period of abnormal growth (at postweaning and juvenile stages) followed by dramatic dendritic atrophy in adulthood. In conclusion, prenatal stress induced significant long-lasting bimodal changes in the morphology of vermal Purkinje cells. These structural alterations, however, were not accompanied by anxious behaviors in the elevated plus maze.

Gender differences in the long-term effects of chronic prenatal stress on the HPA axis and hypothalamic structure in rats

Stress during pregnancy can impair biological and behavioral responses in the adult offspring and some of these effects are associated with structural changes in specific brain regions. Furthermore, these outcomes can vary according to strain, gender, and type and duration of the maternal stress. Indeed, early stress can induce sexually dimorphic long-term effects on diverse endocrine axes, including subsequent responses to stress. However, whether hypothalamic structural modifications are associated with these endocrine disruptions has not been reported. Thus, we examined the gender differences in the long-term effects of prenatal and adult immobilization stress on the hypothalamic-pituitary-adrenocortical (HPA) axis and the associated changes in hypothalamic structural proteins. Pregnant Wistar rats were subjected to immobilization stress three times daily (45 min each) during the last week of gestation. One half of the offspring were subjected to the same regimen of stress on 10 consecutive days starting at postnatal day (PND) 90. At sacrifice (PND 180), serum corticosterone levels were significantly higher in females compared to males and increased significantly in females subjected to both stresses with no change in males. Prenatal stress increased pituitary ACTH content in males, with no effect in females. Hypothalamic CRH mRNA levels were significantly increased by prenatal stress in females, but decreased in male rats. In females neither stress affected hypothalamic cell death, as determined by cytoplasmic histone-associated DNA fragment levels or proliferation, determined by proliferating cell nuclear antigen levels (PCNA); however, in males there was a significant decrease in cell death in response to prenatal stress and a decrease in PCNA levels with both prenatal and adult stress. In all groups BrdU immunoreactivity colocalized in glial fibrillary acidic protein (GFAP) positive cells, with few BrdU/NeuN labelled cells found. Furthermore, in males the astrocyte marker S100β increased with prenatal stress and decreased with adult stress, suggesting affectation of astrocytes. Synapsin-1 levels were increased by adult stress in females and by prenatal stress in males, while, PSD95 levels were increased in females and decreased in males by both prenatal and adult stress. In conclusion, hypothalamic structural rearrangement appears to be involved in the long-term endocrine outcomes observed after both chronic prenatal and adult stresses. Furthermore, many of these changes are not only different between males and females, but opposite, which could underlie the gender differences in the long-term sequelae of chronic stress, including subsequent responses to stress.

Neurodevelopmental animal models of schizophrenia: role in novel drug discovery and development

Schizophrenia is a devastating mental illness that is associated with a lifetime of disability. For patients to successfully function in society, the amelioration of disease symptoms is imperative. The recently published results of two large antipsychotic clinical trials (e.g., CATIE, CUtLASS) clearly exemplified the limitations of currently available treatment options for schizophrenia, and further highlighted the critical need for novel drug discovery and development in this field. One of the biggest challenges in schizophrenia-related drug discovery is to find an appropriate animal model of the illness so that novel hypotheses can be tested at the basic science level. A number of pharmacological, genetic, and neurodevelopmental models have been introduced; however, none of these models has been rigorously evaluated for translational relevance or to satisfy requirements of "face," "construct" and "predictive" validity. Given the apparent polygenic nature of schizophrenia and the limited translational significance of pharmacological models, neurodevelopmental models may offer the best chance of success. The purpose of this review is to provide a general overview of the various neurodevelopmental models of schizophrenia that have been introduced to date, and to summarize their behavioral and neurochemical phenotypes that may be useful from a drug discovery and development standpoint. While it may be that, in the final analysis, no single animal model will satisfy all the requirements necessary for drug discovery purposes, several of the models may be useful for modeling various phenomenological and pathophysiological components of schizophrenia that could be targeted independently with separate molecules or multi-target drugs.

Prenatal stress diminishes gender differences in behavior and in expression of hippocampal synaptic genes and proteins in rats

The study determined whether there were gender differences in the expression of hippocampal genes in adult rats in association with dissimilarity in their behavior, and how these were affected by prenatal stress. Pregnant Wistar rats were subjected to varied stress once daily on days 14-20 of gestation. Adult female offspring of control rats showed significantly less anxiogenic behavior in the elevated plus maze and better discrimination between a novel and familiar object than males in the object recognition test. These gender differences in behavior were markedly attenuated by prenatal stress. Using Affymetrix DNA chip technology on hippocampal extracts prepared from littermates of the offspring used for behavioral tests, we found that 1,680 genes were differentially expressed in control males and females. The gender difference in gene expression was decreased to 11% (191 genes) by prenatal stress. In both sexes, processes like the translational machinery, mitochondrial activity, and cation transport were downregulated compared to controls, but there was a greater suppression of genes involved in vesicle trafficking, regulation of synaptic plasticity, and neurogenesis in females than in males. This was compensated by a higher expression of other components of vesicle trafficking, microtubule-based processes, and neurite development. Prenatal stress decreased the expression of 19 Rab proteins in females and five Rabs in males, but a compensatory increase of Rab partner proteins and effectors only occurred in females. Exposure to stress decreased the expression of synaptic proteins, synaptophysin, and synaptopodin in prenatally stressed males and females and increased those of PSD-95 and NR1 subunit of the N-methyl-D-aspartic acid (NMDA) glutamate receptor only in females. The study provides an unbiased view of key genes and proteins that act as gender dependent molecular sensors. The disruption of their expression by adverse early life stress may explain the alterations that occur in behavior.

Early parental deprivation in the marmoset monkey produces long-term changes in hippocampal expression of genes involved in synaptic plasticity and implicated in mood disorder

In mood disorder, early stressors including parental separation are vulnerability factors, and hippocampal involvement is prominent. In common marmoset monkeys, daily parental deprivation during infancy produces a prodepressive state of increased basal activity and reactivity in stress systems and mild anhedonia that persists at least to adolescence. Here we examined the expression of eight genes, each implicated in neural plasticity and in the pathophysiology of mood disorder, in the hippocampus of these same adolescent marmosets, relative to their normally reared sibling controls. We also measured hippocampal volume. Early deprivation led to decreases in hippocampal growth-associated protein-43 (GAP-43) mRNA, serotonin 1A receptor (5-HT(1A)R) mRNA and binding ([3H]WAY100635), and to increased vesicular GABA transporter mRNA. Brain-derived neurotrophic factor (BDNF), synaptophysin, vesicular glutamate transporter 1 (VGluT1), microtubule-associated protein-2, and spinophilin transcripts were unchanged. There were some correlations with in vivo biochemical and behavioral indices, including VGluT1 mRNA with reward-seeking behavior, and serotonin 1A receptor mRNA with CSF cortisol. Early deprivation did not affect hippocampal volume. We conclude that early deprivation in a nonhuman primate, in the absence of subsequent stressors, has a long-term effect on the hippocampal expression of genes implicated in synaptic function and plasticity. The reductions in GAP-43 and serotonin 1A receptor expressions are comparable with findings in mood disorder, supporting the possibility that the latter reflect an early developmental contribution to disease vulnerability. Equally, the negative results suggest that other features of mood disorder, such as decreased hippocampal volume and BDNF expression, are related to different aspects of the pathophysiological process.