Prenatal bystander stress alters brain, behavior, and the epigenome of developing rat offspring

The role of the placenta-brain axis in psychoneuroimmune programming

Gestational exposures have enduring impacts on brain and neuroimmune development and function. Perturbations of pregnancy leading to placental structure/function deficits, cell stress, immune activation, and endocrine changes (metabolic, growth factors, etc.) all increase neuropsychiatric risk in offspring. The existing literature links obstetric diseases with placental involvement to offspring neuroimmune outcomes and neurodevelopmental risk. Psychoneuroimmune outcomes in offspring brain include changes to microglia, cytokine/chemokine production, cell stress, and long-term immunoreactivity. These outcomes are altered by structural, anti-angiogenic/hypoxic, inflammatory, and metabolic diseases of the placenta. This fetal programming occurs via direct placental passage or production of factors which can act directly on fetal brain substrates, or indirectly via action of circulating factors on intermediates in the placenta. Placental neuroendocrine, vascular/angiogenic, immune, and extracellular vesicular mechanisms are detailed. These mechanisms interact within various placental and pregnancy conditions. An increased understanding of the placental origins of psychoneuroimmunology will yield dividends for human health. Identifying maternal and placental biomarkers for fetal neuroimmune health may also revolutionize early diagnosis and precision psychiatry, empowering patients to make the best healthcare decisions for their families. Targeting placental mechanisms may be a valuable approach for the prevention and mitigation of intergenerational, lifelong neuropathology.

Sex-specific stress and biobehavioral responses to human experimenters in rats

Important factors influencing the outcome of animal experiments in preclinical research are often overlooked. In the current study, the reaction of female and male rats toward the biological sex of a human experimenter was investigated in terms of anxiety-like behaviors and physiological stress responses, as measured by infrared (IR) thermography, circulating corticosterone (CORT) and oxytocin levels. Female rats displayed consistently exacerbated anxiety-related behaviors along with elevated body surface temperature during repeated exposure to male experimenters. Experimental stress further intensified thermal responses to a male experimenter, especially in female rats. The behavioral responses to a male experimenter in females were associated with higher circulating CORT and lower oxytocin levels. Similar responses were induced by a T-shirt worn by a human male. The findings suggest that psychophysiological responses of female rats to a male experimenter are influenced by both visual and olfactory cues. The results emphasize the need to not only consider sex differences in experimental animals, but also standardize and report the experimenter’s biological sex to avoid ambiguity in the generation and interpretation of results.

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.

Biological and Acoustic Sex Differences in Rat Ultrasonic Vocalization

The rat model is a useful tool for understanding peripheral and central mechanisms of laryngeal biology. Rats produce ultrasonic vocalizations (USVs) that have communicative intent and are altered by experimental conditions such as social environment, stress, diet, drugs, age, and neurological diseases, validating the rat model's utility for studying communication and related deficits. Sex differences are apparent in both the rat larynx and USV acoustics and are differentially affected by experimental conditions. Therefore, the purpose of this review paper is to highlight the known sex differences in rat USV production, acoustics, and laryngeal biology detailed in the literature across the lifespan.

Prenatal stress and genetic risk: How prenatal stress interacts with genetics to alter risk for psychiatric illness

Risk for neuropsychiatric disorders is complex and includes an individual's internal genetic endowment and their environmental experiences and exposures. Embryonic development captures a particularly complex period, in which genetic and environmental factors can interact to contribute to risk. These environmental factors are incorporated differently into the embryonic brain than postnatal one. Here, we comprehensively review the human and animal model literature for studies that assess the interaction between genetic risks and one particular environmental exposure with strong and complex associations with neuropsychiatric outcomes-prenatal maternal stress. Gene-environment interaction has been demonstrated for stress occurring during childhood, adolescence, and adulthood. Additional work demonstrates that prenatal stress risk may be similarly complex. Animal model studies have begun to address some underlying mechanisms, including particular maternal or fetal genetic susceptibilities that interact with stress exposure and those that do not. More specifically, the genetic underpinnings of serotonin and dopamine signaling and stress physiology mechanisms have been shown to be particularly relevant to social, attentional, and internalizing behavioral changes, while other genetic factors have not, including some growth factor and hormone-related genes. Interactions have reflected both the diathesis-stress and differential susceptibility models. Maternal genetic factors have received less attention than those in offspring, but strongly modulate impacts of prenatal stress. Priorities for future research are investigating maternal response to distinct forms of stress and developing whole-genome methods to examine the contributions of genetic variants of both mothers and offspring, particularly including genes involved in neurodevelopment. This is a burgeoning field of research that will ultimately contribute not only to a broad understanding of psychiatric pathophysiology but also to efforts for personalized medicine.

Developmental expression of anxiety and depressive behaviours after prenatal predator exposure and early life homecage enhancement

Stressful events during gestation can have sex-specific effects on brain and behaviour, and may contribute to some of the differences observed in adult stress responding and psychopathology. We investigated the impact of a novel repeated prenatal psychological stress (prenatal predator exposure - PPS) during the last week of gestation in rats on offspring behaviours related to social interaction (play behaviour), open field test (OFT), forced swim test (FST) and sucrose preference test (SP) during the juvenile period and in adulthood. We further examined the role of postnatal environmental, using an enhanced housing condition (EHC), to prevent/rescue any changes. Some effects on anxiety, anhedonia, and stress-related coping behaviours (e.g., OFT, SP and OFT) did not emerge until adulthood. PPS increased OFT anxiety behaviours in adult males, and some OFT and SP behaviours in adult females. Contrary to this, EHC had few independent effects; most were apparent only when combined with PPS. In keeping with age-group differences, juvenile behaviours did not necessarily predict the same adult behaviours although juvenile OFT rearing and freezing, and juvenile FST immobility did predict adult FST immobility and sucrose preference, suggesting that some aspects of depressive behaviours may emerge early and predict adult vulnerability or coping behaviours. Together, these results suggest an important, though complex, role for early life psychological stressors and early life behaviours in creating an adult vulnerability to anxiety or depressive disorders and that environmental factors further modulate the effects of the prenatal stressors.

Epigenetic programming by stress and glucocorticoids along the human lifespan

Psychosocial stress triggers a set of behavioral, neural, hormonal, and molecular responses that can be a driving force for survival when adaptive and time-limited, but may also contribute to a host of disease states if dysregulated or chronic. The beneficial or detrimental effects of stress are largely mediated by the hypothalamic-pituitary axis, a highly conserved neurohormonal cascade that culminates in systemic secretion of glucocorticoids. Glucocorticoids activate the glucocorticoid receptor, a ubiquitous nuclear receptor that not only causes widespread changes in transcriptional programs, but also induces lasting epigenetic modifications in many target tissues. While the epigenome remains sensitive to stressors throughout life, we propose two key principles that may govern the epigenetics of stress and glucocorticoids along the lifespan: first, the presence of distinct life periods, during which the epigenome shows heightened plasticity to stress exposure, such as in early development and at advanced age; and, second, the potential of stress-induced epigenetic changes to accumulate throughout life both in select chromatin regions and at the genome-wide level. These principles have important clinical and translational implications, and they show striking parallels with the existence of sensitive developmental periods and the cumulative impact of stressful experiences on the development of stress-related phenotypes. We hope that this conceptual mechanistic framework will stimulate fruitful research that aims at unraveling the molecular pathways through which our life stories sculpt genomic function to contribute to complex behavioral and somatic phenotypes.

Prenatal stressors in rodents: Effects on behavior

The current review focuses on studies in rodents published since 2008 and explores possible reasons for any differences they report in the effects of gestational stress on various types of behavior in the offspring. An abundance of experimental data shows that different maternal stressors in rodents can replicate some of the abnormalities in offspring behavior observed in humans. These include, anxiety, in juvenile and adult rats and mice, assessed in the elevated plus maze and open field tests and depression, detected in the forced swim and sucrose-preference tests. Deficits were reported in social interaction that is suggestive of pathology associated with schizophrenia, and in spatial learning and memory in adult rats in the Morris water maze test, but in most studies only males were tested. There were too few studies on the novel object recognition test at different inter-trial intervals to enable a conclusion about the effect of prenatal stress and whether any deficits are more prevalent in males. Among hippocampal glutamate receptors, NR2B was the only subtype consistently reduced in association with learning deficits. However, like in humans with schizophrenia and depression, prenatal stress lowered hippocampal levels of BDNF, which were closely correlated with decreases in hippocampal long-term potentiation. In mice, down-regulation of BDNF appeared to occur through the action of gene-methylating enzymes that are already increased above controls in prenatally-stressed neonates. In conclusion, the data obtained so far from experiments in rodents lend support to a physiological basis for the neurodevelopmental hypothesis of schizophrenia and depression.

Preconception paternal stress in rats alters dendritic morphology and connectivity in the brain of developing male and female offspring

The goal of this research was to examine the effect of preconception paternal stress (PPS) on the subsequent neurodevelopment and behavior of male and female offspring. Prenatal (gestational) stress has been shown to alter brain morphology in the developing brain, and is presumed to be a factor in the development of some adult psychopathologies. Our hypothesis was that paternal stress in the preconception period could impact brain development in the offspring, leading to behavioral abnormalities later in life. The purpose of this study was to examine the effect of preconception paternal stress on developing male and female offspring brain morphology in five brain areas; medial prefrontal cortex (mPFC), orbitofrontal cortex (OFC), parietal cortex (Par1), hippocampus (CA1) and nucleus accumbens (NAc). Alterations in dendritic measures and spine density were observed in each brain area examined in paternal stress offspring. Our two main findings reveal; (1) PPS alters brain morphology and organization and these effects are different than the effects of stress observed at other ages; and, (2) the observed dendritic changes were sexually dimorphic. This study provides direct evidence that PPS modifies brain architecture in developing offspring, including dendritic length, cell complexity, and spine density. Alterations observed may contribute to the later development of psychopathologies and maladaptive behaviors in the offspring.

Pregnant women's cognitive appraisal of a natural disaster affects DNA methylation in their children 13 years later: Project Ice Storm

Prenatal maternal stress (PNMS) can impact a variety of outcomes in the offspring throughout childhood and persisting into adulthood as shown in human and animal studies. Many of the effects of PNMS on offspring outcomes likely reflect the effects of epigenetic changes, such as DNA methylation, to the fetal genome. However, no animal or human research can determine the extent to which the effects of PNMS on DNA methylation in human offspring is the result of the objective severity of the stressor to the pregnant mother, or her negative appraisal of the stressor or her resulting degree of negative stress. We examined the genome-wide DNA methylation profile in T cells from 34 adolescents whose mothers had rated the 1998 Québec ice storm's consequences as positive or negative (that is, cognitive appraisal). The methylation levels of 2872 CGs differed significantly between adolescents in the positive and negative maternal cognitive appraisal groups. These CGs are affiliated with 1564 different genes and with 408 different biological pathways, which are prominently featured in immune function. Importantly, there was a significant overlap in the differentially methylated CGs or genes and biological pathways that are associated with cognitive appraisal and those associated with objective PNMS as we reported previously. Our study suggests that pregnant women's cognitive appraisals of an independent stressor may have widespread effects on DNA methylation across the entire genome of their unborn children, detectable during adolescence. Therefore, cognitive appraisals could be an important predictor variable to explore in PNMS research.

Sexually dimorphic responses to early adversity: implications for affective problems and autism spectrum disorder

During gestation, development proceeds at a pace that is unmatched by any other stage of the life cycle. For these reasons the human fetus is particularly susceptible not only to organizing influences, but also to pathogenic disorganizing influences. Growing evidence suggests that exposure to prenatal adversity leads to neurological changes that underlie lifetime risks for mental illness. Beginning early in gestation, males and females show differential developmental trajectories and responses to stress. It is likely that sex-dependent organization of neural circuits during the fetal period influences differential vulnerability to mental health problems. We consider in this review evidence that sexually dimorphic responses to early life stress are linked to two developmental disorders: affective problems (greater female prevalence) and autism spectrum disorder (greater male prevalence). Recent prospective studies illustrating the neurodevelopmental consequences of fetal exposure to stress and stress hormones for males and females are considered here. Plausible biological mechanisms including the role of the sexually differentiated placenta are discussed.

Prenatal stress-induced programming of genome-wide promoter DNA methylation in 5-HTT-deficient mice

The serotonin transporter gene (5-HTT/SLC6A4)-linked polymorphic region has been suggested to have a modulatory role in mediating effects of early-life stress exposure on psychopathology rendering carriers of the low-expression short (s)-variant more vulnerable to environmental adversity in later life. The underlying molecular mechanisms of this gene-by-environment interaction are not well understood, but epigenetic regulation including differential DNA methylation has been postulated to have a critical role. Recently, we used a maternal restraint stress paradigm of prenatal stress (PS) in 5-HTT-deficient mice and showed that the effects on behavior and gene expression were particularly marked in the hippocampus of female 5-Htt+/- offspring. Here, we examined to which extent these effects are mediated by differential methylation of DNA. For this purpose, we performed a genome-wide hippocampal DNA methylation screening using methylated-DNA immunoprecipitation (MeDIP) on Affymetrix GeneChip Mouse Promoter 1.0 R arrays. Using hippocampal DNA from the same mice as assessed before enabled us to correlate gene-specific DNA methylation, mRNA expression and behavior. We found that 5-Htt genotype, PS and their interaction differentially affected the DNA methylation signature of numerous genes, a subset of which showed overlap with the expression profiles of the corresponding transcripts. For example, a differentially methylated region in the gene encoding myelin basic protein (Mbp) was associated with its expression in a 5-Htt-, PS- and 5-Htt × PS-dependent manner. Subsequent fine-mapping of this Mbp locus linked the methylation status of two specific CpG sites to Mbp expression and anxiety-related behavior. In conclusion, hippocampal DNA methylation patterns and expression profiles of female prenatally stressed 5-Htt+/- mice suggest that distinct molecular mechanisms, some of which are promoter methylation-dependent, contribute to the behavioral effects of the 5-Htt genotype, PS exposure and their interaction.

DNA methylation signatures triggered by prenatal maternal stress exposure to a natural disaster: Project Ice Storm

BACKGROUND

Prenatal maternal stress (PNMS) predicts a wide variety of behavioral and physical outcomes in the offspring. Although epigenetic processes may be responsible for PNMS effects, human research is hampered by the lack of experimental methods that parallel controlled animal studies. Disasters, however, provide natural experiments that can provide models of prenatal stress.

METHODS

Five months after the 1998 Quebec ice storm we recruited women who had been pregnant during the disaster and assessed their degrees of objective hardship and subjective distress. Thirteen years later, we investigated DNA methylation profiling in T cells obtained from 36 of the children, and compared selected results with those from saliva samples obtained from the same children at age 8.

RESULTS

Prenatal maternal objective hardship was correlated with DNA methylation levels in 1675 CGs affiliated with 957 genes predominantly related to immune function; maternal subjective distress was uncorrelated. DNA methylation changes in SCG5 and LTA, both highly correlated with maternal objective stress, were comparable in T cells, peripheral blood mononuclear cells (PBMCs) and saliva cells.

CONCLUSIONS

These data provide first evidence in humans supporting the conclusion that PNMS results in a lasting, broad, and functionally organized DNA methylation signature in several tissues in offspring. By using a natural disaster model, we can infer that the epigenetic effects found in Project Ice Storm are due to objective levels of hardship experienced by the pregnant woman rather than to her level of sustained distress.

Epigenetic mechanisms in the development of behavior: advances, challenges, and future promises of a new field

In the past decade, there have been exciting advances in the field of behavioral epigenetics that have provided new insights into a biological basis of neural and behavioral effects of gene-environment interactions. It is now understood that changes in the activity of genes established through epigenetic alterations occur as a consequence of exposure to environmental adversity, social stress, and traumatic experiences. DNA methylation in particular has thus emerged as a leading candidate biological pathway linking gene-environment interactions to long-term and even multigenerational trajectories in behavioral development, including the vulnerability and resilience to psychopathology. This paper discusses what we have learned from research using animal models and from studies in which the translation of these findings has been made to humans. Studies concerning the significance of DNA methylation alterations in outcomes associated with stress exposure later in life and dysfunction in the form of neuropsychiatric disorders are highlighted, and several avenues of future research are suggested that promise to advance our understanding of epigenetics both as a mechanism by which the environment can contribute to the development of psychiatric disorders and as an avenue for more effective intervention and treatment strategies.

Harnessing the power of neuroplasticity for intervention

A fundamental property of the brain is its capacity to change with a wide variety of experiences, including injury. Although there are spontaneous reparative changes following injury, these changes are rarely sufficient to support significant functional recovery. Research on the basic principles of brain plasticity is leading to new approaches to treating the injured brain. We review factors that affect synaptic organization in the normal brain, evidence of spontaneous neuroplasticity after injury, and the evidence that factors including postinjury experience, pharmacotherapy, and cell-based therapies, can form the basis of rehabilitation strategies after brain injuries early in life and in adulthood.

Differential methylation of genes in the medial prefrontal cortex of developing and adult rats following exposure to maltreatment or nurturing care during infancy

Quality of maternal care in infancy is an important contributing factor in the development of behavior and psychopathology. One way maternal care could affect behavioral trajectories is through environmentally induced epigenetic alterations within brain regions known to play prominent roles in cognition, emotion regulation, and stress responsivity. Whereas such research has largely focused on the hippocampus or hypothalamus, the prefrontal cortex (PFC) has only just begun to receive attention. The current study was designed to determine whether exposure to maltreatment or nurturing care is associated with differential methylation of candidate gene loci (bdnf and reelin) within the medial PFC (mPFC) of developing and adult rats. Using a within-litter design, infant male and female rats were exposed to an adverse or nurturing caregiving environment outside their home cage for 30 min per day during the first postnatal week. Additional littermates remained with their biological caregiver within the home cage during the manipulations. We observed that infant rats subjected to caregiver maltreatment emitted more audible and ultrasonic vocalizations than littermates subjected to nurturing care either within or outside of the home cage. While we found no maltreatment-induced changes in bdnf DNA methylation present in infancy, sex-specific alterations were present in the mPFC of adolescents and adults that had been exposed to maltreatment. Furthermore, while maltreated females showed differences in reelin DNA methylation that were transient, males exposed to maltreatment and both males and females exposed to nurturing care outside the home cage showed differences in reelin methylation that emerged by adulthood. Our results demonstrate the ability of infant-caregiver interactions to epigenetically mark genes known to play a prominent role in cognition and psychiatric disorders within the mPFC. Furthermore, our data indicate the remarkable complexity of alterations that can occur, with both transient and later emerging DNA methylation differences that could shape developmental trajectories and underlie gender differences in outcomes.

Prenatal exposure to stressful life events is associated with masculinized anogenital distance (AGD) in female infants

In animal models, prenatal stress programs reproductive development in the resulting offspring, however little is known about effects in humans. Anogenital distance (AGD) is a commonly used, sexually dimorphic biomarker of prenatal androgen exposure in many species. In rodents, prenatally stressed males have shorter AGD than controls (suggesting lower prenatal androgen exposure), whereas prenatally stressed females have longer AGD than controls (suggesting greater prenatal androgen exposure). Our objective was to investigate the relationship between stressful life events in pregnancy and infant AGD. In a prospective cohort study, pregnant women and their partners reported exposure to stressful life events during pregnancy. Pregnancies in which the couple reported 4+ life events were considered highly stressed. After birth (average 16.5 months), trained examiners measured AGD in the infants (137 males, 136 females). After adjusting for age, body size and other covariates, females born to couples reporting high stress had significantly longer (i.e. more masculine) AGD than females born to couples reporting low stress (p=0.015). Among males, high stress was weakly, but not significantly, associated with shorter AGD. Our results suggest prenatal stress may masculinize some aspects of female reproductive development in humans. More sensitive measures of prenatal stress and additional measures of reproductive development are needed to better understand these relationships and clarify mechanisms.

Brain plasticity in the developing brain

The developing normal brain shows a remarkable capacity for plastic change in response to a wide range of experiences including sensory and motor experience, psychoactive drugs, parent-child relationships, peer relationships, stress, gonadal hormones, intestinal flora, diet, and injury. The effects of injury vary with the precise age-at-injury, with the general result being that injury during cell migration and neuronal maturation has a poor functional outcome, whereas similar injury during synaptogenesis has a far better outcome. A variety of factors influence functional outcome including the nature of the behavior in question and the age at behavioral assessment as well as pre- and postinjury experiences. Here, we review the phases of brain development, how factors influence brain, and behavioral development in both the normal and perturbed brain, and propose mechanisms that may underlie these effects.

Mechanism of earthquake simulation as a prenatal stressor retarding rat offspring development and chinese medicine correcting the retardation: hormones and gene-expression alteration

We aimed to investigate the mechanism of shaking as a prenatal stressor impacting the development of the offspring and Chinese medicines correcting the alterations. Pregnant rats were randomized into earthquake simulation group (ESG), herbal group (HG) which received herbal supplements in feed after shaking, and control group (CG). Findings revealed body weight and open field test (OFT) score of ESG offspring were statistically inferior to the CG and HG offspring. The corticosterone levels of ESG were higher than those of CG but not than HG. The dopamine level of ESG was slightly lower than that of the CG and of HG was higher than that of ESG. The 5-HT of ESG was higher than CG and HG. The growth hormone level of the ESG was significantly lower than ESG but not than CG. Gene expression profile showed 81 genes upregulated and 39 genes downregulated in ESG versus CG, and 60 genes upregulated and 28 genes downregulated in ESG versus HG. Eighty-four genes were found differentially expressed in ESG versus CG comparison and were normalized in ESG versus HG. We conclude that maternal shaking negatively affected physical and nervous system development, with specific alterations in neurohormones and gene expression. Chinese herbal medicine reduced these negative outcomes.

Experience and the developing prefrontal cortex

The prefrontal cortex (PFC) receives input from all other cortical regions and functions to plan and direct motor, cognitive, affective, and social behavior across time. It has a prolonged development, which allows the acquisition of complex cognitive abilities through experience but makes it susceptible to factors that can lead to abnormal functioning, which is often manifested in neuropsychiatric disorders. When the PFC is exposed to different environmental events during development, such as sensory stimuli, stress, drugs, hormones, and social experiences (including both parental and peer interactions), the developing PFC may develop in different ways. The goal of the current review is to illustrate how the circuitry of the developing PFC can be sculpted by a wide range of pre- and postnatal factors. We begin with an overview of prefrontal functioning and development, and we conclude with a consideration of how early experiences influence prefrontal development and behavior.

Epigenetics and developmental plasticity across species

Plasticity is a typical feature of development and can lead to divergent phenotypes. There is increasing evidence that epigenetic mechanisms, such as DNA methylation, are present across species, are modifiable by the environment, and are involved in developmental plasticity. Thus, in the context of the concept of developmental homology, epigenetic mechanisms may serve to create a process homology between species by providing a common molecular pathway through which environmental experiences shape development, ultimately leading to phenotypic diversity. This article will highlight evidence derived from across-species investigations of epigenetics, development, and plasticity which may contribute to our understanding of the homology that exists between species and between ancestors and descendants.

Prenatal stress produces sexually dimorphic and regionally specific changes in gene expression in hippocampus and frontal cortex of developing rat offspring

Prenatal stress has been known to induce structural changes in the brain and lead to negative psychological well-being. To further understanding of the mechanisms that underlie these effects, whole genome microarray analysis was used to analyze gene expression changes in the developing brain. Epigenetic changes in the hippocampus and frontal cortex of offspring exposed to stress during gestation were investigated. Biological process ontology and pathway analysis was used to increase understanding of the changes produced in response to prenatal stress. The study identified over 700 genes in the frontal cortex and hippocampus that are differentially expressed following prenatal stress. The epigenetic changes demonstrate sex-dependent and region-specific profiles, exhibiting very little overlap between sexes and brain area. Frontal cortex changes were largely related to neurotransmitter function, whereas hippocampal changes were more prominent in females and concentrated around growth factors. These findings have important implications for generalized intervention strategies using a single methodology for all individuals.

Prenatal bystander stress induces neuroanatomical changes in the prefrontal cortex and hippocampus of developing rat offspring

The rapid period of growth and development that occurs prenatally renders the brain vulnerable to experiences that may disrupt cortical plasticity. Although there is extensive literature examining anatomical changes in fully matured brain, there has been very little investigation of younger offspring. The current study used an indirect prenatal bystander stress and analyzed neuroanatomical changes in postnatal day 21 (P21) Long Evans rats. Dendritic architecture (dendritic length, branch order, and spine density) along with cell quantification (neuron and glia) was generated for layer 3 pyramidal cells of the medial prefrontal cortex (mPFC/Cg3), orbital prefrontal cortex (OFC/AID), and CA1 of the hippocampus. We found that prenatal bystander stress significantly altered the complexity and length of dendritic arbor, the density of excitatory spines and the actual volume of neuronal and glial cell numbers in the mPFC, OFC, and CA1 of developing rat offspring. Neuroanatomical changes of this extent occurring at such a critical time period will likely impact healthy maturation of the brain and long-term development.