Long-term effects of prenatal stress on dopamine and glutamate receptors in adult rat brain

Ongoing effects of preterm birth on the dopaminergic and noradrenergic pathways in the frontal cortex and hippocampus of guinea pigs

Children born preterm have an increased likelihood of developing neurobehavioral disorders such as attention-deficit hyperactivity disorder (ADHD) and anxiety. These disorders have a sex bias, with males having a higher incidence of ADHD, whereas anxiety disorder tends to be more prevalent in females. Both disorders are underpinned by imbalances to key neurotransmitter systems, with dopamine and noradrenaline in particular having major roles in attention regulation and stress modulation. Preterm birth disturbances to neurodevelopment may affect this neurotransmission in a sexually dimorphic manner. Time-mated guinea pig dams were allocated to deliver by preterm induction of labor (gestational age 62 [GA62]) or spontaneously at term (GA69). The resultant offspring were randomized to endpoints as neonates (24 h after term-equivalence age) or juveniles (corrected postnatal day 40, childhood equivalence). Relative mRNA expressions of key dopamine and noradrenaline pathway genes were examined in the frontal cortex and hippocampus and quantified with real-time PCR. Myelin basic protein and neuronal nuclei immunostaining were performed to characterize the impact of preterm birth. Within the frontal cortex, there were persisting reductions in the expression of dopaminergic pathway components that occurred in preterm males only. Conversely, preterm-born females had increased expression of key noradrenergic receptors and a reduction of the noradrenergic transporter within the hippocampus. This study demonstrated that preterm birth results in major changes in dopaminergic and noradrenergic receptor, transporter, and synthesis enzyme gene expression in a sex- and region-based manner that may contribute to the sex differences in susceptibility to neurobehavioral disorders. These findings highlight the need for the development of sex-based treatments for improving these conditions.

Neurosteroids and the mesocorticolimbic system

The mesocorticolimbic system coordinates executive functions, such as working memory and behavioral flexibility. This circuit includes dopaminergic projections from the ventral tegmental area to the nucleus accumbens and medial prefrontal cortex. In this review, we summarize evidence that cells in multiple nodes of the mesocorticolimbic system produce neurosteroids (steroids synthesized in the nervous system) and express steroid receptors. Here, we focus on neuroandrogens (androgens synthesized in the nervous system), neuroestrogens (estrogens synthesized in the nervous system), and androgen and estrogen receptors. We also summarize how (neuro)androgens and (neuro)estrogens affect dopamine signaling in the mesocorticolimbic system and regulate executive functions. Taken together, the data suggest that steroids produced in the gonads and locally in the brain modulate higher-order cognition and executive functions.

The hyperexcitability of laterodorsal tegmentum cholinergic neurons accompanies adverse behavioral and cognitive outcomes of prenatal stress

Exposure to prenatal stress (PS) leads to the offspring's vulnerability towards the development of cognitive and behavioral disorders. Laterodorsal tegmentum (LDT) is a part of the brainstem cholinergic system that is believed to play a pivotal role in the stress-associated progression of anxiety, memory impairment, and addictive behaviors. In this study, we aimed to investigate the electrophysiological alterations of LDT cholinergic neurons and its accompanied behavioral and cognitive outcomes in the offspring of mice exposed to physical or psychological PS. Swiss Webster mice were exposed to physical or psychological stress on the tenth day of gestation. Ex vivo investigations in LDT brain slices of adolescent male offspring were performed to evaluate the effects of two stressor types on the activity of cholinergic neurons. Open field test, elevated plus maze, passive avoidance test, and conditioned place preference were conducted to assess behavioral and cognitive alterations in the offspring. The offspring of both physical and psychological PS-exposed mice exhibited increased locomotor activity, anxiety-like behavior, memory impairment, and preference to morphine. In both early- and late-firing cholinergic neurons of the LDT, stressed groups demonstrated higher firing frequency, lower adaptation ratio, decreased action potential threshold, and therefore increased excitability compared to the control group. The findings of the present study suggest that the hyperexcitability of the cholinergic neurons of LDT might be involved in the development of PS-associated anxiety-like behaviors, drug seeking, and memory impairment.

Maternal Immune Activation and Enriched Environments Impact B2 SINE Expression in Stress Sensitive Brain Regions of Rodent Offspring

Early life stress (ELS) can have wide-spread neurodevelopmental effects with support accumulating for the idea that genomic mechanisms may induce lasting physiological and behavioral changes following stress exposure. Previous work found that a sub-family of transposable elements, SINEs, are repressed epigenetically after acute stress. This gives support to the concept that the mammalian genome may be regulating retrotransposon RNA expression allowing for adaptation in response to environmental challenges, such as maternal immune activation (MIA). Transposon (TE) RNAs are now thought to work at the epigenetic level and to have an adaptive response to environmental stressors. Abnormal expression of TEs has been linked to neuropsychiatric disorders like schizophrenia, which is also linked to maternal immune activation. Environmental enrichment (EE), a clinically utilized intervention, is understood to protect the brain, enhance cognitive performance, and attenuate responses to stress. This study examines the effects of MIA on offspring B2 SINE expression and further, the impact that EE, experienced throughout gestation and early life, may have in conjunction with MIA during development. Utilizing RT-PCR to quantify the expression of B2 SINE RNA in the juvenile brain of MIA exposed rat offspring, we found dysregulation of B2 SINE expression associated with MIA in the prefrontal cortex. For offspring experiencing EE, the prefrontal cortex exhibited an attenuation of the MIA response observed in standard housed animals. Here, the adaptive nature of B2 is observed and thought to be aiding in the animal's adaptation to stress. The present changes indicate a wide-spread stress-response system adaptation that impacts not only changes at the genomic level but potentially observable behavioral impacts throughout the lifespan, with possible translational relevance to psychotic disorders.

Long-term behavioral effects of prenatal stress in the Fmr1-knock-out mouse model for fragile X syndrome

Fragile X syndrome (FXS) is a major neurodevelopmental disorder and the most common monogenic cause of autism spectrum disorder (ASD). FXS is caused by a mutation in the X-linked FMR1 gene leading to the absence of the FMRP protein, inducing several behavioral deficits, including motor, emotional, cognitive, and social abnormalities. Beside its clear genetic origins, FXS can be modulated by environmental factors, e.g., stress exposure: indeed the behavioral phenotype of FXS, as well as of ASD patients can be exacerbated by the repeated experience of stressful events, especially early in life. Here we investigated the long-term effects of prenatal exposure to unpredictable chronic stress on the behavioral phenotype of the Fmr1-knock-out (KO) mouse model for FXS and ASD. Mice were tested for FXS- and ASD-relevant behaviors first at adulthood (3 months) and then at aging (18 months), in order to assess the persistence and the potential time-related progression of the stress effects. Stress induced the selective emergence of behavioral deficits in Fmr1-KO mice that were evident in spatial memory only at aging. Stress also exerted several age-specific behavioral effects in mice of both genotypes: at adulthood it enhanced anxiety levels and reduced social interaction, while at aging it enhanced locomotor activity and reduced the complexity of ultrasonic calls. Our findings underline the relevance of gene-environment interactions in mouse models of neurodevelopmental syndromes and highlight the long-term behavioral impact of prenatal stress in laboratory mice.

The effects of early life stress on impulsivity

Elevated impulsivity is a symptom shared by various psychiatric disorders such as substance use disorder, bipolar disorder, and attention-deficit/hyperactivity disorder. However, impulsivity is not a unitary construct and impulsive behaviors fall into two subcategories: impulsive action and impulsive choice. Impulsive choice refers to the tendency to prefer immediate, small rewards over delayed, large rewards, whereas impulsive action involves difficulty inhibiting rash, premature, or mistimed behaviors. These behaviors are mediated by the mesocorticolimbic dopamine (DA) system, which consists of projections from the ventral tegmental area to the nucleus accumbens and prefrontal cortex. Early life stress (ELS) alters both impulsive choice and impulsive action in rodents. ELS also changes DA receptor expression, transmission, and activity within the mesocorticolimbic system. This review integrates the dopamine, impulsivity, and ELS literature to provide evidence that ELS alters impulsivity via inducing changes in the mesocorticolimbic DA system. Understanding how ELS affects brain circuits associated with impulsivity can help advance treatments aimed towards reducing impulsivity symptoms in a variety of psychiatric disorders.

Resilience to Stress: Lessons from Rodents about Nature versus Nurture

Individual differences in human temperament influence how we respond to stress and can confer vulnerability (or resilience) to emotional disorders. For example, high levels of behavioral inhibition in children predict increased risk of mood and anxiety disorders in later life. The biological underpinnings of temperament are unknown, although improved understanding can offer insight into the pathogenesis of emotional disorders. Our laboratory has used a rat model of temperamental differences to study neurodevelopmental factors that lead to a highly inhibited, stress vulnerable phenotype. Selective breeding for high versus low behavioral response to novelty created two rat strains that exhibit dramatic behavior differences over multiple domains relevant to emotional disorders. Low novelty responder (bLR) rats exhibit high levels of behavioral inhibition, passive stress coping, anhedonia, decreased sociability and vulnerability to chronic stress compared to high novelty responders (bHRs). On the other hand, bHRs exhibit high levels of behavioral dis-inhibition, active coping, and aggression. This review article summarizes our work with the bHR/bLR model showing the developmental emergence of the bHR/bLR phenotypes, the role the environment plays in shaping it, and the involvement of epigenetic processes such as DNA methylation that mediate differences in emotionality and stress reactivity.

The effect of oxytocin and an enriched environment on anxiety-like behaviour and corticosterone levels in a prenatally stressed febrile seizure rat model

Background

Febrile seizures (FS) are a neurological abnormality which occur following a fever that has resulted from a systemic infection and are characterised by convulsions. These convulsions occur due to abnormally increased signalling of interleukin-1 beta, resulting in increased neuronal hyper-excitability. Furthermore, exposure to prenatal stress has been shown to exacerbate seizure duration, elicit anxiety-like behaviour and corticosterone levels. Oxytocin is a neuropeptide with anxiolytic, social bonding, and stress regulation effects. Therefore, the aim of the study was to assess whether oxytocin can attenuate the anxiety-like behaviour and increased corticosterone in rat offspring exposed to prenatal stress and FS.

Method

Sprague Dawley rats were mated. On GND14, prenatal stress was induced on pregnant dams for 1 hr/7 days. On PND 14, rat pups were injected with lipopolysaccharide (LPS, 200 μg/kg, i.p.) followed 2.5 h later by an i.p. injection of kainic acid (KA, 1.75 mg/kg). Oxytocin (1 mg/kg) was induced via different routes (intraperitoneal or intranasal) as well an enriched environment between PND 22-26. The enriched environment included larger cages (1560 cm²) with only 4 pups per cage, compared to those groups not receiving enrichment (646 cm²), as well as cardboard rolls and plastic toys. On PND 27-33 the light/dark box and elevated plus maze were used to assess anxiety-like behaviour. On PND 34 all rats were euthanized using a sharp guillotine, trunk blood and hypothalamic tissue were collected for neurochemical analysis (ELISA kit).

Results

Our findings confirmed that exposure to both prenatal stress and febrile seizures resulted anxiety-like behaviour and significantly higher plasma corticosterone concentrations compared to their counterparts. Environmental enrichment was significantly effective in attenuating the increased basal corticosterone levels and anxiety-like behaviour seen in the prenatally stressed FS rat. Although direct administration of oxytocin showed higher significance in reducing corticosterone plasma levels when compared to the enriched environment. Furthermore, hypothalamic oxytocin levels were not significant in rat exposed to environmental enrichment while oxytocin treatment showed a significant effect when compared to their counterparts.

Conclusion

Therefore, oxytocin administration during early postnatal development shows great potential in reversing the effects of prenatal stress and its subsequent exacerbation of FS.

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.

Prenatally stress-exposed male rats present lower theta prefrontal activity during attention behaviors to receptive females

Prenatal stress affects brain functionality and sexual behavior. The medial prefrontal cortex (mPFC) participates in the integration and processing of sexual stimuli. Electroencephalographic (EEG) theta activity has been associated with attention as well as rewarding and sexually motivated states. Considering that the induction of sexual motivation requires attention to, and the adequate processing of, sexual stimuli, this study aimed to evaluate the effects of exposure to stress during the prenatal period on EEG activity in the mPFC during nose pokes in adulthood, actions which are indicators of attention to a receptive female. Eighteen sexually experienced male rats were used, nine stressed prenatally by immobilization during days 14-21 of gestation (stress-exposed group). The other nine formed the control group. All rats were implanted bilaterally in the mPFC (specifically in prelimbic areas) and were allowed one intromission with a receptive female to induce a sexually motivated state before the experimental session. During this session, both nose pokes and non-contact erections in the male rats were evaluated in the presence of an inaccessible receptive female. EEGs were recorded only during nose pokes. The stress-exposed group presented lower nose poke duration, fewer non-contact erections, and lower relative power of the theta band (4-7 Hz) in both prefrontal areas. Considering that the prevalence of this band is associated with attention and motivational processes, these data confirm the deleterious effect of prenatal stress on attention and sexual activation to sexually relevant stimuli in male rats during adulthood.

Prenatal stress and increased susceptibility to anxiety-like behaviors: role of neuroinflammation and balance between GABAergic and glutamatergic transmission

Neuroplasticity during the prenatal period allows neurons to regenerate anatomically and functionally for re-programming the brain development. During this critical period of fetal programming, the fetus phenotype can change in accordance with environmental stimuli such as stress exposure. Prenatal stress (PS) can exert important effects on brain development and result in permanent alterations with long-lasting consequences on the physiology and behavior of the offspring later in life. Neuroinflammation, as well as GABAergic and glutamatergic dysfunctions, has been implicated as potential mediators of behavioral consequences of PS. Hyperexcitation, due to enhanced excitatory transmission or reduced inhibitory transmission, can promote anxiety. Alterations of the GABAergic and/or glutamatergic signaling during fetal development lead to a severe excitatory/inhibitory imbalance in neuronal circuits, a condition that may account for PS-precipitated anxiety-like behaviors. This review summarizes experimental evidence linking PS to an elevated risk to anxiety-like behaviors and interprets the role of the neuroinflammation and alterations of the brain GABAergic and glutamatergic transmission in this phenomenon. We hypothesize this is an imbalance in GABAergic and glutamatergic circuits (as a direct or indirect consequence of neuroinflammation), which at least partially contributes to PS-precipitated anxiety-like behaviors and primes the brain to be vulnerable to anxiety disorders. Therefore, pharmacological interventions with anti-inflammatory activities and with regulatory effects on the excitatory/inhibitory balance can be attributed to the novel therapeutic target for anxiety disorders.

Prenatal Stress Leads to the Altered Maturation of Corticostriatal Synaptic Plasticity and Related Behavioral Impairments Through Epigenetic Modifications of Dopamine D2 Receptor in Mice

Prenatal stress (PRS) had a long-term adverse effect on motor behaviors. Corticostriatal synaptic plasticity, a cellular basis for motor controlling, has been proven to participate in the pathogenesis of many behavior disorders. Based on the reports about the involvement of epigenetic DNA alterations in PRS-induced long-term effects, this research investigated the influence of PRS on the development and maturation of corticostriatal synaptic plasticity and related behaviors and explored the underlying epigenetic mechanism. Subjects were male offspring of dams that were exposed to stress three times per day from the 10th day of pregnancy until delivery. The development and maturation of plasticity at corticostriatal synapses, dopamine signaling, behavioral habituation, and DNA methylation were examined and analyzed. Control mice expressed long-term potentiation (LTP) at corticostriatal synapses during postnatal days (PD) 12-14 and produced long-term depression (LTD) during PD 20-60. However, PRS mice exhibited sustained LTP during PD 12-60. The treatment with dopamine 2 receptor (D2R) agonist quinpirole recovered striatal LTD and improved the impaired behavioral habituation in PD 45 adult PRS mice. Additionally, adult PRS mice showed reduced D2R, excess DNA methyltransferase 1 (DNMT1), increased binding of DNMT1 to D2R promoter, and hypermethylation at D2R promoter in the striatum. The DNMT1 inhibitor 5-aza-deoxycytidine restored striatal synaptic plasticity and improved behavioral habituation in adult PRS mice via D2R-mediated dopamine signaling. DNMT1-associated D2R hypermethylation is responsible for altering the maturation of plasticity at corticostriatal synapses and impairing the behavioral habituation in PRS mice.

Anti-Stress Properties of Atypical Antipsychotics

Stress exposure represents a major environmental risk factor for schizophrenia and other psychiatric disorders, as it plays a pivotal role in the etiology as well as in the manifestation of disease symptomatology. It may be inferred that pharmacological treatments must be able to modulate the behavioral, functional, and molecular alterations produced by stress exposure to achieve significant clinical outcomes. This review aims at examining existing clinical and preclinical evidence that supports the ability of atypical antipsychotic drugs (AAPDs) to modulate stress-related alterations. Indeed, while the pharmacodynamic differences between AAPDs have been extensively characterized, less is known on their ability to regulate downstream mechanisms that are critical for functional recovery and patient stabilization. We will discuss stress-related mechanisms, spanning from neuroendocrine function to inflammation and neuronal plasticity, which are relevant for the manifestation of schizophrenic symptomatology, and we will discuss if and how AAPDs may interfere with such mechanisms. Considering the impact of stress in everyday life, we believe that a better understanding of the potential effects of AAPDs on stress-related mechanisms may provide novel and important insights for improving therapeutic strategies aimed at promoting coping mechanisms and enhancing the quality of life of patients affected by psychiatric disorders.

Microglial memory of early life stress and inflammation: Susceptibility to neurodegeneration in adulthood

We review evidence supporting the role of early life programming in the susceptibility for adult neurodegenerative diseases while highlighting questions and proposing avenues for future research to advance our understanding of this fundamental process. The key elements of this phenomenon are chronic stress, neuroinflammation triggering microglial polarization, microglial memory and their connection to neurodegeneration. We review the mediating mechanisms which may function as early biomarkers of increased susceptibility for neurodegeneration. Can we devise novel early life modifying interventions to steer developmental trajectories to their optimum?

Photoperiodic effects on monoamine signaling and gene expression throughout development in the serotonin and dopamine systems

Photoperiod or the duration of daylight has been implicated as a risk factor in the development of mood disorders. The dopamine and serotonin systems are impacted by photoperiod and are consistently associated with affective disorders. Hence, we evaluated, at multiple stages of postnatal development, the expression of key dopaminergic (TH) and serotonergic (Tph2, SERT, and Pet-1) genes, and midbrain monoamine content in mice raised under control Equinox (LD 12:12), Short winter-like (LD 8:16), or Long summer-like (LD 16:8) photoperiods. Focusing in early adulthood, we evaluated the midbrain levels of these serotonergic genes, and also assayed these gene levels in the dorsal raphe nucleus (DRN) with RNAScope. Mice that developed under Short photoperiods demonstrated elevated midbrain TH expression levels, specifically during perinatal development compared to mice raised under Long photoperiods, and significantly decreased serotonin and dopamine content throughout the course of development. In adulthood, Long photoperiod mice demonstrated decreased midbrain Tph2 and SERT expression levels and reduced Tph2 levels in the DRN compared Short photoperiod mice. Thus, evaluating gene × environment interactions in the dopaminergic and serotonergic systems during multiple stages of development may lead to novel insights into the underlying mechanisms in the development of affective disorders.

Hyperexcitability of VTA dopaminergic neurons in male offspring exposed to physical or psychological prenatal stress

Prenatal stress (PS) exposure leads to cognitive and behavioral alterations in offspring including an increased risk of substance abuse and anxiety disorders. Signalling from dopamine (DA) neurons of the ventral tegmental area (VTA) in the mesoaccumbal and mesocortical pathways plays a vital role in drug dependency and anxiety behavior. To provide further knowledge about the changes in drug seeking behavior and anxiety behaviors in prenatally stressed mice, we conducted ex vivo investigations in VTA brain slices of adult male PS offspring to evaluate the effects of two types of PS (physical vs. psychological) on activity of DA neurons. Elevated plus maze (EPM) was used to assess anxiety-like behaviors and conditioned place preference (CPP) was used to evaluate drug reinforcing effects in mice. An increased anxiety-like behavior and preference to morphine was observed in prenatally stressed mice. PS VTA DA cells exhibited greater I_h current and a higher frequency and amplitude of sEPSCs, which were consistent with a greater degree of pre- or postsynaptic excitability of the VTA. This was confirmed by lower rheobase and lower firing thresholds in PS VTA neurons, as well as increases in spontaneous firing frequency. When taken together, these data suggest that alterations in VTA DA neurons in this mouse model of prenatal stress might be associated with later life alterations in drug seeking and anxiety-like behaviors through their role in mesocortical and mesoaccumbal pathways.

Pre-clinical models of reward deficiency syndrome: A behavioral octopus

Individuals with mood disorders or with addiction, impulsivity and some personality disorders can share in common a dysfunction in how the brain perceives reward, where processing of natural endorphins or the response to exogenous dopamine stimulants is impaired. Reward Deficiency Syndrome (RDS) is a polygenic trait with implications that suggest cross-talk between different neurological systems that include the known reward pathway, neuroendocrine systems, and motivational systems. In this review we evaluate well-characterized animal models for their construct validity and as potential models for RDS. Animal models used to study substance use disorder, major depressive disorder (MDD), early life stress, immune dysregulation, attention deficit hyperactivity disorder (ADHD), post traumatic stress disorder (PTSD), compulsive gambling and compulsive eating disorders are discussed. These disorders recruit underlying reward deficiency mechanisms in multiple brain centers. Because of the widespread and remarkable array of associated/overlapping behavioral manifestations with a common root of hypodopaminergia, the basic endophenotype recognized as RDS is indeed likened to a behavioral octopus. We conclude this review with a look ahead on how these models can be used to investigate potential therapeutics that target the underlying common deficiency.

Potential frameworks to support evaluation of mechanistic data for developmental neurotoxicity outcomes: A symposium report

A key challenge in systematically incorporating mechanistic data into human health assessments is that, compared to studies of apical health endpoints, these data are both more abundant (mechanistic studies routinely outnumber other studies by several orders of magnitude) and more heterogeneous (e.g. different species, test system, tissue, cell type, exposure paradigm, or specific assays performed). A structured decision-making process for organizing, integrating, and weighing mechanistic DNT data for use in human health risk assessments will improve the consistency and efficiency of such evaluations. At the Developmental Neurotoxicology Society (DNTS) 2016 annual meeting, a symposium was held to address the application of existing organizing principles and frameworks for evaluation of mechanistic data relevant to interpreting neurotoxicology data. Speakers identified considerations with potential to advance the use of mechanistic DNT data in risk assessment, including considering the context of each exposure, since epigenetics, tissue type, sex, stress, nutrition and other factors can modify toxicity responses in organisms. It was also suggested that, because behavior is a manifestation of complex nervous system function, the presence and absence of behavioral change itself could be used to organize the interpretation of multiple complex simultaneous mechanistic changes. Several challenges were identified with frameworks and their implementation, and ongoing research to develop these approaches represents an early step toward full evaluation of mechanistic DNT data for assessments.

Lineage- and Sex-Dependent Behavioral and Biochemical Transgenerational Consequences of Developmental Exposure to Lead, Prenatal Stress, and Combined Lead and Prenatal Stress in Mice

BACKGROUND

Lead (Pb) exposure and prenatal stress (PS) during development are co-occurring risk factors with shared biological substrates. PS has been associated with transgenerational passage of altered behavioral phenotypes, whereas the transgenerational behavioral or biochemical consequences of Pb exposure, and modification of any such effects by PS, is unknown.

OBJECTIVES

The present study sought to determine whether Pb, PS, or combined Pb and PS exposures produced adverse transgenerational consequences on brain and behavior.

METHODS

Maternal Pb and PS exposures were carried out in F0 mice. Outside breeders were used at each subsequent breeding, producing four F1-F2 lineages: [F1 female-F2 female (FF), FM (male), MF, and MM]. F3 offspring were generated from each of these lineages and examined for outcomes previously found to be altered by Pb, PS, or combined Pb and PS in F1 offspring: behavioral performance [fixed-interval (FI) schedule of food reward, locomotor activity, and anxiety-like behavior], dopamine function [striatal expression of tyrosine hydroxylase (Th)], glucocorticoid receptor (GR) and plasma corticosterone, as well as brain-derived neurotrophic factor (BDNF) and total percent DNA methylation of Th and Bdnf genes in the frontal cortex and hippocampus.

RESULTS

Maternal F0 Pb exposure produced runting in F3 offspring. Considered across lineages, F3 females exhibited Pb-related alterations in behavior, striatal BDNF levels, frontal cortical Th total percentage DNA methylation levels and serum corticosterone levels, whereas F3 males showed Pb- and PS-related alterations in behavior and total percent DNA methylation of hippocampal Bdnf. However, numerous lineage-specific effects were observed, most of greater magnitude than those observed across lineages, with outcomes differing by F3 sex.

DISCUSSION

These findings support the possibility that exposures of previous generations to Pb or PS may influence the brain and behavior of future generations. Observed changes were sex-dependent, with F3 females showing multiple changes through Pb-exposed lineages. Lineage effects may occur through maternal responses to pregnancy, altered maternal behavior, epigenetic modifications, or a combination of mechanisms, but they have significant public health ramifications regardless of mechanism. https://doi.org/10.1289/EHP4977.

Influence of prenatal transportation stress-induced differential DNA methylation on the physiological control of behavior and stress response in suckling Brahman bull calves

The objective of this experiment was to examine potential differential methylation of DNA as a mechanism for altered behavioral and stress responses in prenatally stressed (PNS) compared with nonprenatally stressed (Control) young bull calves. Mature Brahman cows (n = 48) were transported for 2-h periods at 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 d of gestation (Transported group) or maintained as nontransported Controls (n = 48). From the offspring born to Transported and Control cows, a subset of 28-d-old intact bulls (n = 7 PNS; n = 7 Control) were evaluated for methylation of DNA of behavior and stress response-associated genes. Methylation of DNA from white blood cells was assessed via reduced representation bisulfite sequencing methods. Because increased methylation of DNA within gene promoter regions has been associated with decreased transcriptional activity of the corresponding gene, differentially methylated (P ≤ 0.05) CG sites (cytosine followed by a guanine nucleotide) located within promoter regions (n = 1,205) were used to predict (using Ingenuity Pathway Analysis software) alterations to canonical pathways in PNS compared with Control bull calves. Among differentially methylated genes (P ≤ 0.05) related to behavior and the stress response were OPRK1, OPRM1, PENK, POMC, NR3C2, TH, DRD1, DRD5, COMT, HTR6, HTR5A, GABRA4, GABRQ, and GAD2. Among altered (P < 0.05) signaling pathways related to behavior and the stress response were Opioid Signaling, Corticotropin-Releasing Hormone Signaling, Dopamine Receptor Signaling, Dopamine-DARPP32 Feedback in cAMP Signaling, Serotonin Receptor Signaling, and GABA Receptor Signaling. Alterations to behavior and stress response-related genes and canonical pathways supported previously observed elevations in temperament score and serum cortisol through weaning in the larger population of PNS calves from which bulls in this study were derived. Differential methylation of DNA and predicted alterations to behavior and stress response-related pathways in PNS compared with Control bull calves suggest epigenetic programming of behavior and the stress response in utero.

Prenatal Glucocorticoid Exposure Results in Changes in Gene Transcription and DNA Methylation in the Female Juvenile Guinea Pig Hippocampus Across Three Generations

Synthetic glucocorticoids (sGC) are administered to women at risk for pre-term delivery, to mature the fetal lung and decrease neonatal morbidity. sGC also profoundly affect the fetal brain. The hippocampus expresses high levels of glucocorticoid (GR) and mineralocorticoid receptor (MR), and its development is affected by elevated fetal glucocorticoid levels. Antenatal sGC results in neuroendocrine and behavioral changes that persist in three generations of female guinea pig offspring of the paternal lineage. We hypothesized that antenatal sGC results in transgenerational changes in gene expression that correlate with changes in DNA methylation. We used RNASeq and capture probe bisulfite sequencing to investigate the transcriptomic and epigenomic effects of antenatal sGC exposure in the hippocampus of three generations of juvenile female offspring from the paternal lineage. Antenatal sGC exposure (F₀ pregnancy) resulted in generation-specific changes in hippocampal gene transcription and DNA methylation. Significant changes in individual CpG methylation occurred in RNApol II binding regions of small non-coding RNA (snRNA) genes, which implicates alternative splicing as a mechanism involved in transgenerational transmission of the effects of antenatal sGC. This study provides novel perspectives on the mechanisms involved in transgenerational transmission and highlights the importance of human studies to determine the longer-term effects of antenatal sGC on hippocampal-related function.

Prenatal stress and elevated seizure susceptibility: Molecular inheritable changes

Stressful episodes are common during early-life and may have a wide range of negative effects on both physical and mental status of the offspring. In addition to various neurobehavioral complications induced by prenatal stress (PS), seizure is a common complication with no fully explained cause. In this study, the association between PS and seizure susceptibility was reviewed focusing on sex differences and various underlying mechanisms. The role of drugs in the initiation of seizure and the effects of PS on the nervous system that prone the brain for seizure, especially the hypothalamic-pituitary-adrenal (HPA) axis, are also discussed in detail by reviewing the papers studying the effect of PS on glutamatergic, gamma-aminobutyric acid (GABA)ergic, and adrenergic systems in the context of seizure and epilepsy. Finally, epigenetic changes in epilepsy are described, and the underlying mechanisms of this change are expanded. As the effects of PS may be life-lasting, it is possible to prevent future psychiatric and behavioral disorders including epilepsy by preventing avoidable PS risk factors.

Diagnostic Testing for Equine Endocrine Diseases: Confirmation Versus Confusion

Despite there being only 2 common endocrine diseases in horses, pituitary pars intermedia dysfunction (PPID) and equine metabolic syndrome (EMS), diagnosis is still confusing. Failing to consider horse factors and treating based on laboratory results only have caused many animals to receive lifelong drug treatment unnecessarily. Increased plasma ACTH, baseline or TRH stimulated, supports a diagnosis of PPID; however, breed, age, thriftiness, illness, coat color, geography, diet, and season also affect ACTH concentration. Insulin dysregulation, the hallmark of EMS, can result from insulin resistance or excessive postprandial insulin release. Each requires a different diagnostic test to reach a diagnosis.

Altered DNA Methylation in the Developing Brains of Rats Genetically Prone to High versus Low Anxiety

There is growing evidence of abnormal epigenetic processes playing a role in the neurobiology of psychiatric disorders, although the precise nature of these anomalies remains largely unknown. To study neurobiological (including epigenetic) factors that influence emotionality, we use rats bred for distinct behavioral responses to novelty. Rats bred for low novelty response (low responder [LR]) exhibit high levels of anxiety- and depressive-like behavior compared with high novelty responder (HR) rats. Prior work revealed distinct limbic brain development in HR versus LR rats, including altered expression of genes involved in DNA methylation. This led us to hypothesize that DNA methylation differences in the developing brain drive the disparate HR/LR neurobehavioral phenotypes. Here we report altered DNA methylation markers (altered DNA methyltransferase protein levels and increased global DNA methylation levels) in the early postnatal amygdala of LR versus HR male rats. Next-generation sequencing methylome profiling identified numerous differentially methylated regions across the genome in the early postnatal HR/LR amygdala. We also contrasted methylation profiles of male HRs and LRs with a control rat strain that displays an intermediate behavioral phenotype relative to the HR/LR extremes; this revealed that the LR amygdalar methylome was abnormal, with the HR profile more closely resembling that of the control group. Finally, through two methylation manipulations in early life, we found that decreasing DNA methylation in the developing male and female amygdala improves adult anxiety- and depression-like behavior. These findings suggest that inborn DNA methylation differences play important roles in shaping brain development and lifelong emotional behavior.SIGNIFICANCE STATEMENT Epigenetic changes are biological mechanisms that regulate the expression and function of genes throughout the brain and body. DNA methylation, one type of epigenetic mechanism, is known to be altered in brains of psychiatric patients, which suggests a role for DNA methylation in the pathogenesis of psychiatric disorders, such as depression and anxiety. The present study examines brains of rats that display high versus low levels of anxiety- and depression-like behavior to investigate how neural DNA methylation levels differ in these animals and how such differences shape their emotional behavioral differences. Studying how epigenetic processes affect emotional behavior may improve our understanding of the neurobiology of psychiatric disorders and lead to improved treatments.

Prenatal transportation stress alters genome-wide DNA methylation in suckling Brahman bull calves

The objective of this experiment was to identify genome-wide differential methylation of DNA in young prenatally stressed (PNS) bull calves. Mature Brahman cows (n = 48) were transported for 2-h periods at 60 ± 5, 80 ± 5, 100 ± 5, 120 ± 5, and 140 ± 5 d of gestation or maintained as nontransported Controls (n = 48). Methylation of DNA from white blood cells from a subset of 28-d-old intact male offspring (n = 7 PNS; n = 7 Control) was assessed via reduced representation bisulfite sequencing. Samples from PNS bulls contained 16,128 CG, 226 CHG, and 391 CHH (C = cytosine; G = guanine; H = either adenine, thymine, or cytosine) sites that were differentially methylated compared to samples from Controls. Of the CG sites, 7,407 were hypermethylated (at least 10% more methylated than Controls; P ≤ 0.05) and 8,721 were hypomethylated (at least 10% less methylated than Controls; P ≤ 0.05). Increased DNA methylation in gene promoter regions typically results in decreased transcriptional activity of the region. Therefore, differentially methylated CG sites located within promoter regions (n = 1,205) were used to predict (using Ingenuity Pathway Analysis software) alterations to canonical pathways in PNS compared with Control bull calves. In PNS bull calves, 113 pathways were altered (P ≤ 0.05) compared to Controls. Among these were pathways related to behavior, stress response, metabolism, immune function, and cell signaling. Genome-wide differential DNA methylation and predicted alterations to pathways in PNS compared with Control bull calves suggest epigenetic programming of biological systems in utero.

Effects of Interaction Between DRD4 Methylation and Prenatal Maternal Stress on Methylphenidate-Induced Changes in Continuous Performance Test Performance in Youth with Attention-Deficit/Hyperactivity Disorder

OBJECTIVES

Environmental factors may interact with genetic factors via the epigenetic process, and this interaction can contribute to inter-individual variability in the treatment response. The purpose of this study was to investigate the interaction effects between dopamine receptor D4 (DRD4) methylation and prenatal maternal stress on the methylphenidate (MPH) response of youth with attention-deficit/hyperactivity disorder (ADHD).

METHODS

This study was an 8-week open-label trial of MPH that included 74 ADHD youth. We investigated the associations between MPH treatment response, which was defined as a score ≤2 on the Clinical Global Impressions-Improvement (CGI-I) scale, and the methylation of 28 cytosine-guanine dinucleotide (CpG) sites of DRD4. Additionally, the interaction effects between DRD4 methylation and prenatal maternal stress on changes in Continuous Performance Test (CPT) scores after MPH treatment were investigated.

RESULTS

Although there were no significant sites that showed significant association with treatment response, there was a significant interaction effect of the methylation of CpG7 and prenatal maternal stress on changes in omission errors of the CPT following treatment (p = 0.0001).

CONCLUSIONS

The present findings indicate that the interaction between methylation of CpG7 of DRD4 and prenatal maternal stress may be predictive of the treatment response to MPH in youth with ADHD.

Is the risk of low birth weight or preterm labor greater when maternal stress is experienced during pregnancy? A systematic review and meta-analysis of cohort studies

Antenatal stress is linked to fetal risks that increase the chances of neonatal complications and reduction of child cognitive ability. Therefore, we aimed to evaluate if maternal stress affects fetal, neonatal or child development. The following databases were searched: MEDLINE (1966 to May 2016), Embase (1980 to May 2016), LILACS (1982 to May 2016) and CENTRAL (1972 to May 2016). Observational studies published in English and Portuguese were included whether there was any relationship between fetal and neonatal outcome, such as birth weight, preterm labor, child development with pregnant women that were subjected to any stress type during at least one month of follow-up. Two independent reviewers screened eligible articles, extracted data and assessed the risk of bias. Thus, 8 cohort studies with about 8,271 pregnant women and 1,081,151 children proved eligible. Results suggested a significant association between antenatal stress exposure and increasing rates of low birth weight (Odds ratio (OR) 1.68 [95% Confidential Interval (CI) 1.19, 2.38]). However, there was no statistically significance difference between non-exposed and exposed groups related to preterm labor (OR 1.98 [95% CI 0.91 to 4.31]; I2 = 68%, p = 0.04). Although, results were inconsistent with primary analysis suggesting a significant association between antenatal stress exposure and the occurrence of higher rates of preterm birth (OR 1.42 [95% CI 1.05 to 1.91]; I2 = 68%, p = 0.04) in the sensitivity analysis. Furthermore, the current review has suggested that stress perceived during antenatal negatively influences fetal life and child development. Yet, further studies are necessary with adequate sample size and longer follow-up time to confirm our findings.

Non-invasive biomarkers of fetal brain development reflecting prenatal stress: An integrative multi-scale multi-species perspective on data collection and analysis

Prenatal stress (PS) impacts early postnatal behavioural and cognitive development. This process of 'fetal programming' is mediated by the effects of the prenatal experience on the developing hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS). We derive a multi-scale multi-species approach to devising preclinical and clinical studies to identify early non-invasively available pre- and postnatal biomarkers of PS. The multiple scales include brain epigenome, metabolome, microbiome and the ANS activity gauged via an array of advanced non-invasively obtainable properties of fetal heart rate fluctuations. The proposed framework has the potential to reveal mechanistic links between maternal stress during pregnancy and changes across these physiological scales. Such biomarkers may hence be useful as early and non-invasive predictors of neurodevelopmental trajectories influenced by the PS as well as follow-up indicators of success of therapeutic interventions to correct such altered neurodevelopmental trajectories. PS studies must be conducted on multiple scales derived from concerted observations in multiple animal models and human cohorts performed in an interactive and iterative manner and deploying machine learning for data synthesis, identification and validation of the best non-invasive detection and follow-up biomarkers, a prerequisite for designing effective therapeutic interventions.

Endocrine active metals, prenatal stress and enhanced neurobehavioral disruption

Metals, including lead (Pb), methylmercury (MeHg) and arsenic (As), are long-known developmental neurotoxicants. More recently, environmental context has been recognized to modulate metals toxicity, including nutritional state and stress exposure. Modulation of metal toxicity by stress exposure can occur through shared targeting of endocrine systems, such as the hypothalamic-pituitary-adrenal axis (HPA). Our previous rodent research has identified that prenatal stress (PS) modulates neurotoxicity of two endocrine active metals (EAMs), Pb and MeHg, by altering HPA and CNS systems disrupting behavior. Here, we review this research and further test the hypothesis that prenatal stress modulates metals neurotoxicity by expanding to test the effect of developmental As ± PS exposure. Serum corticosterone and behavior was assessed in offspring of dams exposed to As ± PS. PS increased female offspring serum corticosterone at birth, while developmental As exposure decreased adult serum corticosterone in both sexes. As + PS induced reductions in locomotor activity in females and reduced response rates on a Fixed Interval schedule of reinforcement in males, with the latter suggesting unique learning deficits only in the combined exposure. As-exposed males showed increased time in the open arms of an elevated plus maze and decreased novel object recognition whereas females did not. These data further confirm the hypothesis that combined exposure to chemical (EAMs) and non-chemical (PS) stressors results in enhanced neurobehavioral toxicity. Given that humans are exposed to multiple environmental risk factors that alter endocrine function in development, such models are critical for risk assessment and public health protection, particularly for children.

Neurotrophins and neuroinflammation in fetuses exposed to maternal depression and anxiety disorders during pregnancy: a comparative study on cord blood

In recent years, there have been changes in the approach to maternal psychiatric disorders and their effects on the fetus, with the focus redirected to the search for biological markers. Neurotrophic factors and inflammatory processes have received particular attention in the past few years. According to the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), the study sample (n = 136) consisted of three groups: mothers with major depressive disorder (MDD group, n = 25), mothers with anxiety disorder (AD group, n = 18), and mothers without any psychiatric disorders (not diagnosed (ND) group, n = 93). During the delivery/cesarean section, a blood sample was obtained from the umbilical cord. Serum concentrations of BDNF, NT-3, FGF2, TNF-α, and neopterin were determined by enzyme-linked immunosorbent assay (ELISA), according to the manufacturer's procedure. Clinical and biochemical characteristics were assessed. We did not find a significant difference among the three study groups with regard to BDNF, NT-3, and TNF-α levels. The ANOVA test indicated statistically significant differences in FGF2 levels and neopterin between the study groups. The newborns of mothers with AD had significantly higher FGF2 levels and significantly higher neopterin levels when compared with those of mothers with MDD and healthy mothers. The present study sheds light on the effects of higher FGF2 and neopterin levels in fetuses exposed to AD. Our results should be replicated through further prospective studies with a larger sample size.

Perinatal Psychoneuroimmunology: Protocols for the Study of Prenatal Stress and Its Effects on Fetal and Postnatal Brain Development

Prenatal stress (PS) impacts early behavioral, neuroimmune, and cognitive development. Pregnant rat models have been very valuable in examining the mechanisms of such fetal programming. A newer pregnant sheep model of maternal stress offers the unique advantages of chronic in utero monitoring and manipulation. This chapter presents the techniques used to model single and multigenerational stress exposures and their pleiotropic effects on the offspring.

Are changes in excitability in the hippocampus of adult male rats induced by prenatal methamphetamine exposure or stress?

Prenatal stress and drug exposure induce permanent alterations of the brain. Even though different brain structures are involved, alterations almost always refer to the hippocampus. The aim of this study was to investigate the excitability of hippocampal slices in low-magnesium epilepsy model of prenatally methamphetamine (MA, 5mg/kg sc.) or saline (sc., stress model) exposed animals in adult male rats. The second aim was to investigate, if a low dose of MA (1ml/kgs.c.) administered in adulthood changes the hippocampal activity of these animals. Adult Wistar male rats were divided into groups according to their prenatal treatment (C - naïve control; Sa - saline; MA - MA administration). One half of the animals was treated with a challenge dose of MA (1mg/kg sc.) 45min before hippocampal slices were cut. The activity of 350μ thick transversal slices of CA1 hippocampi was recorded (latencies of the first epileptiform discharge and the regular epileptiform activity) and evaluated in ACSF with low-magnesium concentration. Effects of prenatal exposure: The highest excitability was found in the Sa (prenatally stressed) group in respect to C and MA groups. This group developed also the highest number of seizure-like events. In addition, the prenatally MA treated group had also higher excitability than C group. Effects of the MA challenge dose: The challenge dose decreased the excitability of prenatally SA- exposed group. To conclude, even a mild prenatal stress significantly increases hippocampal excitability in adulthood and a challenge dose of MA is able to dampen it.

Sex- and brain region- specific effects of prenatal stress and lead exposure on permissive and repressive post-translational histone modifications from embryonic development through adulthood

Developmental exposure to prenatal stress (PS) and lead (Pb) can affect brain development and adversely influence behavior and cognition. Epigenetic-based gene regulation is crucial for normal brain development and mis-regulation, in any form, can result in neurodevelopmental disorders. Post-translational histone modifications (PTHMs) are an integral and dynamic component of the epigenetic machinery involved in gene regulation. Exposures to Pb and/or PS may alter PTHM profiles, promoting lifelong alterations in brain function observed following Pb±PS exposure. Here we examined the effects of Pb±PS on global levels of activating marks H3K9Ac and H3K4Me3 and repressive marks H3K9Me2 and H3K27Me3 at different developmental stages: E18, PND0, PND6 and PND60. Dams were exposed to 0 or 100ppm Pb beginning 2 months prior to breeding followed by no PS (NS) or PS resulting in 4 offspring treatment groups per sex: 0-NS (control), 0-PS, 100-NS and 100-PS. Global levels of PTHMs varied from E18 through adulthood even in control mice, and were influenced by sex and brain-region. The developmental trajectory of these PTHM levels was further modified by Pb±PS in a sex-, brain region- and age-dependent manner. Females showed a preferential response to Pb alone in frontal cortex (FC) and differentially to PS alone and combined Pb+PS in hippocampus (HIPP). In males, PS-induced increases in PTHM levels in FC, whereas PS produced reductions in HIPP. Pb±PS-based changes in PTHM levels continued to be observed in adulthood (PND60), demonstrating the lasting effect of these early life environmental events on these histone marks. These results indicate that epigenetic consequences of Pb±PS and their contribution to mechanisms of toxicity are sex dependent. Additional studies will assist in understanding the functional significance of these changes in PTHM levels on expression of individual genes, functional pathways, and ultimately, their behavioral consequences.

Hypercaloric diet prevents sexual impairment induced by maternal food restriction

Prenatal undernutrition impairs copulatory behavior and increases the tendency to become obese/overweight, which also reduces sexual behavior. Re-feeding rats prenatally undernourished with a normocaloric diet can restore their physiological conditions and copulatory behavior. Thus, the present study investigated whether a hypercaloric diet that is administered in rats during the juvenile period prevents sexual impairments that are caused by maternal food restriction and the tendency to become overweight/obese. Female rats were prenatally fed a 40% restricted diet from gestational day 2 to 18. The pups received a hypercaloric diet from postnatal day (PND) 23 to PND65 (food restricted hypercaloric [FRH] group) or laboratory chow (food restricted control [FRC] group). Pups from non-food-restricted dams received laboratory chow during the entire experiment (non-food-restricted [NFR] group). During the juvenile period and adulthood, body weight gain was evaluated weekly. The day of balanopreputial separation, sexual behavior, sexual organ weight, hypodermal adiposity, striatal dopamine and serotonin, serum testosterone, and tumor necrosis factor α (TNF-α) were evaluated. The FRH group exhibited an increase in body weight on PND58 and PND65. The FRC group exhibited an increase in the latency to the first mount and intromission and an increase in serum TNF-α levels but a reduction of dopaminergic activity. The hypercaloric diet reversed all of these effects but increased adiposity. We concluded that the hypercaloric diet administered during the juvenile period attenuated reproductive impairments that were induced by maternal food restriction through increases in the energy expenditure but not the tendency to become overweight/obese.

Maternal administration of magnesium sulfate promotes cell proliferation in hippocampus dentate gyrus in offspring mice after exposing to prenatal stress

Prenatal stress (PS) inhibits cell proliferation in the hippocampal dentate gyrus (DG), which is related to hippocampal anatomy and function abnormality. The aim of the study was to investigate the effects of magnesium sulfate (MgSO₄) on PS-induced cell proliferation suppression in offspring during embryonic stage and postnatal spatial learning. MgSO₄ administration was performed after PS treatment on pregnant mice. Mice were randomly divided into four groups: non-PS or PS maternal mice injected with MgSO₄ or saline (P+NS, P+MG, C+MG and C+NS group). Corticosterone was collected from amniotic fluid of mother mice on day 17 of embryonic stage (E17). The ability for spatial learning and memory of pups postnatal 3 week was evaluated using water maze assay. Additionally, cell proliferation was detected by assessing the expression of Ki67 using immunohistochemistry in mice fetuses or pups. PS significantly increased corticosterone level in amniotic fluid (P<0.05) and impaired the spatial learning and memory (P+NS vs C+NS of latency time and track path length: P<0.05) of offspring on postnatal day 21. However, MgSO₄ administration could reverse PS-induced spatial learning and memory disability (P+MG vs P+NS, P<0.05). Additionally, PS reduced the number of Ki67-positive cell in hippocampal DG on E17, E19 and postnatal day 21 (P+NS vs C+NS, P<0.05), which were also abrogated by maternal administration of MgSO₄ (P+MG vs P+NS, P<0.05). Collectively, prenatal administration of MgSO₄ can reverse PS-induced reduction of cell proliferation in hippocampal DG during embryonic stage and postnatal spatial learning.

Long-term consequences of prenatal stress and neurotoxicants exposure on neurodevelopment

There is a large consensus that the prenatal environment determines the susceptibility to pathological conditions later in life. The hypothesis most widely accepted is that exposure to insults inducing adverse conditions in-utero may have negative effects on the development of target organs, disrupting homeostasis and increasing the risk of diseases at adulthood. Several models have been proposed to investigate the fetal origins of adult diseases, but although these approaches hold true for almost all diseases, particular attention has been focused on disorders related to the central nervous system, since the brain is particularly sensitive to alterations of the microenvironment during early development. Neurobiological disorders can be broadly divided into developmental, neurodegenerative and neuropsychiatric disorders. Even though most of these diseases share genetic risk factors, the onset of the disorders cannot be explained solely by inheritance. Therefore, current understanding presumes that the interactions of environmental input, may lead to different disorders. Among the insults that can play a direct or indirect role in the development of neurobiological disorders are stress, infections, drug abuse, and environmental contaminants. Our laboratories have been involved in the study of the neurobiological impact of gestational stress on the offspring (Dr. Antonelli's lab) and on the effect of gestational exposure to toxicants, mainly methyl mercury (MeHg) and perfluorinated compounds (PFCs) (Dr. Ceccatelli's lab). In this focused review, we will review the specialized literature but we will concentrate mostly on our own work on the long term neurodevelopmental consequences of gestational exposure to stress and neurotoxicants.

Sex-dependent effects of lead and prenatal stress on post-translational histone modifications in frontal cortex and hippocampus in the early postnatal brain

Environmental lead (Pb) exposure and prenatal stress (PS) are co-occurring risk factors for impaired cognition and other disorders/diseases in adulthood and target common biological substrates in the brain. Sex-dependent differences characterize the neurochemical and behavioral responses of the brain to Pb and PS and sexually dimorphic histone modifications have been reported to occur in at-risk brain regions (cortex and hippocampus) during development. The present study sought to examine levels and developmental timing of sexually dimorphic histone modifications (i.e., H3K9/14Ac and H3K9Me3) and the extent to which they may be altered by Pb±PS. Female C57/Bl6 mice were randomly assigned to receive distilled deionized drinking water containing 0 or 100ppm Pb acetate for 2 months prior to breeding and throughout lactation. Half of the dams in each group were exposed to restraint stress (PS, three restraint sessions in plastic cylindrical devices 3×/day at for 30min/day (1000, 1300, and 1600h)) from gestational day 11-19 or no stress (NS). At delivery (PND0) and postnatal day 6 (PND6), pups were euthanized and frontal cortex and hippocampus were removed, homogenized, and assayed for levels of H3K9/14Ac and H3K9Me3. Sex-dependent differences in both levels of histone modifications as well as the developmental trajectory of changes in these levels were observed in both structures and these parameters were differentially affected by Pb±PS in a sex and brain-region-dependent manner. Disruptions of these epigenetic processes by developmental Pb±PS may underlie some of the sex-dependent neurobehavioral differences previously observed in these animals.