Effects of prenatal stress on maternal behavior in the rat

Prenatal restraint stress affects early neurobehavioral response and oxidative stress in mice pups

Prenatal stress (PS), in both humans and animals, presents a potential risk to the mother and her fetus throughout gestation. PS is always associated with physiological changes that alter embryonic development and predispose the individual to lifelong health problems, including susceptibility to mental illness. This study aims to identify the harmful effects of prenatal restraint stress (PRS), commonly employed to induce stress painlessly and without any lasting debilitation during gestation. This stress is applied to pregnant Swiss albino mice from E7.5 to delivery for three hours daily. Our results show that PS affects dams' weight gain during the gestational period; moreover, the PS dams prefer passive nursing, exhibit a lower percentage of licking and grooming, and impair other maternal behaviors, including nesting and pup retrieval. Concerning the offspring, this stress induces neurobehavioral impairments, including a significant increase in the time of recovery of the young stressed pups in the surface righting reflex, the latency to avoid the cliff in the cliff avoidance test, longer latencies to accomplish the task in negative geotaxis, and a lower score in swimming development. These alterations were accompanied by increased Malondialdehyde activity (MDA) at PND17 and 21 and downregulation of AchE activity in the whole brain of pups on postnatal days 7 and 9. These findings demonstrated that PS causes deleterious neurodevelopmental impairments that can alter various behaviors later in life.

Dam (Canis familiaris) Welfare throughout the Peri-Parturient Period in Commercial Breeding Kennels

Simple Summary

Welfare problems experienced during gestation and lactation may negatively affect dams and their puppies. However, the welfare states of dams in commercial breeding (CB) kennels during this period have not been well examined. Therefore, we examined a range of behavioral, physical, and physiological metrics throughout the period around parturition to identify if changes indicative of impaired welfare were present. We tested 74 dams from eight CB kennels at 6 and 1 week prepartum, and 4 and 8 weeks postpartum. At each time point we measured their responses to a stranger approaching, their physical health, and indicators of their stress response, immune function, and parasite burden. Findings did not reveal major changes in dam welfare. Most changes observed were likely because of natural biological changes resulting from pregnancy, lactation, and weaning. However, as some changes in metrics deviated from what was expected and there were changes in environmental and management factors during this time, future research should identify how they affect dam welfare.

Abstract

Poor dam welfare throughout the peri-parturient period can also negatively affect that of their offspring. This study aimed to identify changes in physical, physiological, and behavioral metrics indicative of dam welfare throughout the peri-parturient period. Dams (n = 74) from eight U.S. Midwest commercial breeding (CB) kennels were tested at 6 and 1 week prepartum, and 4 and 8 weeks postpartum. At each time point dams underwent a stranger approach test, physical health assessment, hair collection for hair cortisol concentration (HCC) and fecal collection for fecal glucocorticoid metabolites (FGM), fecal secretory immunoglobulin A (sIgA) and parasite detection. Linear mixed-effects models indicated dams exhibited more affiliative behaviors towards the stranger at 4 weeks postpartum than 6 weeks prepartum (p = 0.03), increased HCC from 4-weeks to 8 weeks postpartum (p = 0.02), and increased FGM from 1 week prepartum to 8 weeks postpartum (p = 0.04). At each respective time point, the percentage of dams with intestinal parasites was 11%, 4%, 23%, and 15%. Most changes are likely due to increased energy requirements and hormonal variations. However, deviations from expected changes may have resulted from changes in environment and/ or management, which should be explored in future studies.

Effects of music exposure during pregnancy on maternal behavior in mother rats

Several studies have demonstrated the possibility of positive effects of exposure to music during pregnancy on mental function in humans and animals. Although there remains a core belief in the positive effects of music during pregnancy, the underlying neurobehavioral mechanisms of these effects remain unknown. In this study, we aimed to clarify the relationship between maternal nurturing behavior and the oxytocinergic system to elucidate the effect of music on mental health during pregnancy in an experimental investigation using animal models. Pregnant rats were exposed to Mozart sonatas, and their nurturing behavior after delivery was assessed using behavioral analyses. The neural activities of the oxytocinergic system, which are associated with nurturing behavior, were investigated using FosB immunohistochemistry. Music during pregnancy significantly increased the licking behavior of mothers towards pups, which is representative of positive nurturing behavior. In contrast, this alteration in maternal behavior was shown to have no marked effect on the structure or activity of the oxytocinergic system. This study provided possible evidence that exposure to music during pregnancy had a positive effect on postnatal maternal behavior. The results also suggest that the oxytocinergic system, considered a strong candidate for the neural system that regulates maternal behavior, may not be associated with this behavioral change. Understanding the relationship between other neural systems, physiological responses, and nurturing behaviors will provide a more comprehensive explanation of the mechanisms by which music exposure during pregnancy has a positive effect on mental health.

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Pregnant rats were exposed to Mozart sonatas and their nurturing behavior was investigated.

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Exposure to music during pregnancy has a positive effect on postnatal maternal behavior.

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Maternal behavior had no marked effect on the structure or activity of the oxytocinergic neurons.

What's wrong with my experiment?: The impact of hidden variables on neuropsychopharmacology research

The field of neuropsychopharmacology relies on behavioral assays to quantify behavioral processes related to mental illness and substance use disorders. Although these assays have been highly informative, sometimes laboratories have unpublished datasets from experiments that "didn't work". Often this is because expected outcomes were not observed in positive or negative control groups. While this can be due to experimenter error, an important alternative is that under-appreciated environmental factors can have a major impact on results. "Hidden variables" such as circadian cycles, husbandry, and social environments are often omitted in methods sections, even though there is a strong body of literature documenting their impact on physiological and behavioral outcomes. Applying this knowledge in a more critical manner could provide behavioral neuroscientists with tools to develop better testing methods, improve the external validity of behavioral techniques, and make better comparisons of experimental data across institutions. Here we review the potential impact of "hidden variables" that are commonly overlooked such as light-dark cycles, transport stress, cage ventilation, and social housing structure. While some of these conditions may not be under direct control of investigators, it does not diminish the potential impact of these variables on experimental results. We provide recommendations to investigators on which variables to report in publications and how to address "hidden variables" that impact their experimental results.

Prenatal stress enhances atherosclerosis and telomere shortening in ApoE knockout mouse offspring

Children born to women who experience stress during pregnancy have an increased risk of atherosclerosis in later life, but few animal models have explored mechanisms. To study this phenomena, timed-bred ApoE knockout mice were determined pregnant with ultrasound and randomly assigned on gestation day 8.5 to either a control (no stress) or prenatal stress (PS) group using two hours of restraint for five consecutive days. PS significantly increased plasma corticosterone levels in pregnant mice. The litters from PS mice showed increased neonatal mortality within the first week of life. Body weights (at euthanasia) of adult offspring at 25 weeks from the PS group were significantly increased compared to weights of controls. Adult offspring from these pregnancies were serially imaged with ultrasound to measure plaque thickness and were compared with plaque macro- and microscopic pathology. PS groups had increased plaques thickness by ultrasound, gross, histological evaluation and increased aortic root and valve macrophage infiltration at 25 weeks. Five-week old mice from PS group had significant decrease in mean arterial pressure, yet blood pressure normalized by 10 weeks. Since prenatal stress induced increased atherosclerosis, and telomeres are susceptible to stress, aortas from 10 week old mice were compared for telomere lengths and were found to be significantly shorter in PS mice compared to control mice. These studies support future investigation of how stress impacts telomere shortening in animal models and human aortas. This model could be further utilized to investigate the role of prenatal stress, telomere biology and atherosclerosis pathogenesis in adults.

Gestational stress alters maternal behavior and inflammatory markers in the olfactory bulb of lactating mice

Inflammatory markers represent important candidates responsible for the altered behavior and physiology observed after stressful experiences. In the maternal brain, the olfactory bulb (OB) is a key constituent of the neural circuit that mediates the reciprocal interaction between mother and infant. This study aimed to investigate the effects of stress during pregnancy on maternal behavior and inflammatory changes in the olfactory bulb of lactating mice. Female Balb/c mice were divided into two groups: control (CT) and restraint stress (RS). Maternal behavior was performed during the first 8 days of life of the offspring. On the 10th day after parturition, corticosterone, gene, and protein expression were assessed. Stress during pregnancy decreased the maternal index at postnatal day 4 and the nuclear factor-κB 1 (NFκB1) gene expression in the OB. Moreover, females from the RS group showed increased interleukin (IL-1β) protein expression. In contrast, stressed females exhibited a decreased tumor necrosis factor (TNF-α) protein expression in the OB. In conclusion, exposure to stress during pregnancy was able to induce specific postnatal effects on maternal behavior and balance of inflammatory mediators in the OB.

Early-Life Stress Reprograms Stress-Coping Abilities in Male and Female Juvenile Rats

Prenatal stress (PS) is a major risk factor for the development of emotional disorders in adulthood that may be mediated by an altered hypothalamic-pituitary-adrenal axis response to stress. Although the early onset of stress-related disorders is recognized as a major public health problem, to date, there are relatively few studies that have examined the incidence of early-life stressors in younger individuals. In this study, we assessed PS impact on the stress-coping response of juvenile offspring in behavioral tests and in the induced molecular changes in the hippocampus. Furthermore, we assessed if pregnancy stress could be driving changes in patterns of maternal behavior during early lactation. We found that PS modified stress-coping abilities of both sex offspring. In the hippocampus, PS increased the expression of bdnf-IV and crfr1 and induced sex difference changes on glucocorticoids and BDNF mRNA receptor levels. PS changed the hippocampal epigenetic landscape mainly in male offspring. Stress during pregnancy enhanced pup-directed behavior of stressed dams. Our study indicates that exposure to PS, in addition to enhanced maternal behavior, induces dynamic neurobehavioral variations at juvenile ages of the offspring that should be considered adaptive or maladaptive, depending on the characteristics of the confronting environment. Our present results highlight the importance to further explore risk factors that appear early in life that will be important to allow timely prevention strategies to later vulnerability to stress-related disorders.

Maternal stress effects on infant development in wild Verreaux's sifaka (Propithecus verreauxi)

Abstract

Maternal effects mediated by nutrients or specific endocrine states of the mother can affect infant development. Specifically, pre- and postnatal maternal stress associated with elevated glucocorticoid (GC) output is known to influence the phenotype of the offspring, including their physical and behavioral development. These developmental processes, however, remain relatively poorly studied in wild vertebrates, including primates with their relatively slow life histories. Here, we investigated the effects of maternal stress, assessed by fecal glucocorticoid output, on infant development in wild Verreaux’s sifakas (Propithecus verreauxi), a group-living Malagasy primate. In a first step, we investigated factors predicting maternal fecal glucocorticoid metabolite (fGCM) concentrations, how they impact infants’ physical and behavioral development during the first 6 months of postnatal life as well as early survival during the first 1.5 years of postnatal life. We collected fecal samples of mothers for hormone assays and behavioral data of 12 infants from two birth cohorts, for which we also assessed growth rates. Maternal fGCM concentrations were higher during the late prenatal but lower during the postnatal period compared to the early/mid prenatal period and were higher during periods of low rainfall. Infants of mothers with higher prenatal fGCM concentrations exhibited faster growth rates and were more explorative in terms of independent foraging and play. Infants of mothers with high pre- and postnatal fGCM concentrations were carried less and spent more time in nipple contact. Time mothers spent carrying infants predicted infant survival: infants that were more carried had lower survival, suggesting that they were likely in poorer condition and had to be cared for longer. Thus, the physical and behavioral development of these young primates were impacted by variation in maternal fGCM concentrations during the first 6 months of their lives, presumably as an adaptive response to living in a highly seasonal, but unpredictable environment.

Significance statement

The early development of infants can be impacted by variation in maternal condition. These maternal effects can be mediated by maternal stress (glucocorticoid hormones) and are known to have downstream consequences for behavior, physiology, survival, and reproductive success well into adulthood. However, the direction of the effects of maternal physiological GC output on offspring development is highly variable, even within the same species. We contribute comparative data on maternal stress effects on infant development in a Critically Endangered primate from Madagascar. We describe variation in maternal glucocorticoid output as a function of ecological and reproductive factors and show that patterns of infant growth, behavioral development, and early survival are predicted by maternal glucocorticoids. Our study demonstrates how mothers can influence offspring fitness in response to challenging environmental conditions.

Mothers' neural response to valenced infant interactions predicts postpartum depression and anxiety

It is currently unknown whether differences in neural responsiveness to infant cues observed in postpartum affective disturbance are specific to depression/anxiety or are better attributed to a common component of internalizing distress. It is also unknown whether differences in mothers’ brain response can be accounted for by effects of past episodes, or if current neural processing of her child may serve as a risk factor for development of future symptoms. Twenty-four mothers from a community-based sample participated in an fMRI session viewing their 3-month- old infant during tasks evoking positive or negative emotion. They were tracked across the ensuing 15 months to monitor changes in affective symptoms. Past and current episodes of depression and anxiety, as well as future symptoms, were used to predict differences in mothers’ hemodynamic response to their infant in positive compared to negative emotion contexts. Lower relative activation in largely overlapping brain regions involving frontal lobe structures to own infant positive vs. negative emotion was associated with concurrent (3-month) depression diagnosis and prospective (3–18 month) depression and anxiety symptoms. There was little evidence for impacts of past psychopathology (more limited effect of past anxiety and nonsignificant effect of past depression). Results suggest biased maternal processing of infant emotions during postpartum depression and anxiety is largely accounted for by a shared source of variance (internalizing distress). Furthermore, differential maternal responsiveness to her infant’s emotional cues is specifically associated with the perpetuation of postpartum symptoms, as opposed to more general phenotypic or scarring effects of past psychopathology.

Decoupling the effects of food and density on life-history plasticity of wild animals using field experiments: Insights from the steward who sits in the shadow of its tail, the North American red squirrel

Long-term studies of wild animals provide the opportunity to investigate how phenotypic plasticity is used to cope with environmental fluctuations and how the relationships between phenotypes and fitness can be dependent upon the ecological context. Many previous studies have only investigated life-history plasticity in response to changes in temperature, yet wild animals often experience multiple environmental fluctuations simultaneously. This requires field experiments to decouple which ecological factor induces plasticity in fitness-relevant traits to better understand their population-level responses to those environmental fluctuations. For the past 32 years, we have conducted a long-term integrative study of individually marked North American red squirrels Tamiasciurus hudsonicus Erxleben in the Yukon, Canada. We have used multi-year field experiments to examine the physiological and life-history responses of individual red squirrels to fluctuations in food abundance and conspecific density. Our long-term observational study and field experiments show that squirrels can anticipate increases in food availability and density, thereby decoupling the usual pattern where animals respond to, rather than anticipate, an ecological change. As in many other study systems, ecological factors that can induce plasticity (such as food and density) covary. However, our field experiments that manipulate food availability and social cues of density (frequency of territorial vocalizations) indicate that increases in social (acoustic) cues of density in the absence of additional food can induce similar life-history plasticity, as does experimental food supplementation. Changes in the levels of metabolic hormones (glucocorticoids) in response to variation in food and density are one mechanism that seems to induce this adaptive life-history plasticity. Although we have not yet investigated the energetic response of squirrels to elevated density or its association with life-history plasticity, energetics research in red squirrels has overturned several standard pillars of knowledge in physiological ecology. We show how a tractable model species combined with integrative studies can reveal how animals cope with resource fluctuations through life-history plasticity.

Prenatal urban traffic noise exposure impairs spatial learning and memory and reduces glucocorticoid receptor expression in the hippocampus of male rat offspring

Introduction

Exposure to noise stress during early life may permanently affect the structure and function of the central nervous system. The aim of this study was to evaluate the effects of prenatal exposure to urban traffic noise on the spatial learning and memory of the rats' offspring and the expression of glucocorticoid receptors (GRs) in their hippocampi.

Methods

Three g\roups of pregnant rats were exposed to recorded urban traffic noise for 1, 2 or 4 h/day during the last week of pregnancy. At the age of 45 days, their male offspring were introduced to the Morris water maze (MWM) for assessment of spatial learning and memory. The corticosterone levels were measured in the offspring's sera by radioimmunoassay, and the relative expression of glucocorticoid and mineralocorticoid receptors (MRs) in their hippocampi was evaluated via RT-PCR.

Results

Facing urban traffic noise for 2 and 4 h/day during the third trimester of pregnancy caused the offspring to spend more time and to travel a larger distance than the controls to find the target platform. Analogously, these two groups were inferior to their control counterparts in the probe test. Also, prenatal noise stress elevated the corticosterone concentration in the sera of the rats' offspring and dose-dependently decreased the relative expression of the mRNA of both GRs and MRs in their hippocampi.

Conclusions

Urban traffic noise exposure during the last trimester of pregnancy impairs spatial learning and memory of rat offspring and reduces GRs and MRs gene expression in the hippocampus.

Effects of sleep restriction during pregnancy on postpartum maternal behavior in female rats

Preclinical studies evaluating the effects of gestational sleep restriction on maternal behavior are needed in order to provide information on the background mechanisms underlying this relationship. In this study, 32 female 90 days-old Wistar-Hannover rats were distributed in two groups: Control group (CTRL - n = 13), not subjected to any manipulation during pregnancy; and sleep restriction group (SR - n = 19) - subjected to sleep restriction during the whole pregnancy (21 days). Maternal behavioral analysis was conducted from postpartum day 1 (PPD1) to PPD7, based on observational ethograms. On PPD11 the animals were subjected to the grooming analysis algorithm, followed by the elevated plus maze. Results from an ethogram-based analysis indicated a decrease in self-grooming among sleep-deprived rats (denoting reduced anxiety-like behavior), but no significant differences were found in maternal behavior (except for a slight increase in high arched-back nursing). Controlled analysis detected an impairment in high-arched back nursing in sleep-deprived animals. The grooming microstructure analysis showed an increased frequency of incorrect transitions among sleep restricted animals, indicating increased anxiety-like behavior. No significant differences were observed in the elevated-plus maze. In conclusion, sleep-restricted pregnant rats display an equivalent or slightly increased maternal behavior during the postpartum period, when compared to control animals.

Targeting the Stress System During Gestation: Is Early Handling a Protective Strategy for the Offspring?

The perinatal window is a critical developmental time when abnormal gestational stimuli may alter the development of the stress system that, in turn, influences behavioral and physiological responses in the newborns. Individual differences in stress reactivity are also determined by variations in maternal care, resulting from environmental manipulations. Despite glucocorticoids are the primary programming factor for the offspring's stress response, therapeutic corticosteroids are commonly used during late gestation to prevent preterm negative outcomes, exposing the offspring to potentially aberrant stress reactivity later in life. Thus, in this study, we investigated the consequences of one daily s.c. injection of corticosterone (25 mg/kg), from gestational day (GD) 14-16, and its interaction with offspring early handling, consisting in a brief 15-min maternal separation until weaning, on: (i) maternal behavior; and (ii) behavioral reactivity, emotional state and depressive-like behavior in the adolescent offspring. Corticosterone plasma levels, under non-shock- and shock-induced conditions, were also assessed. Our results show that gestational exposure to corticosterone was associated with diminished maternal care, impaired behavioral reactivity, increased emotional state and depressive-like behavior in the offspring, associated with an aberrant corticosterone response. The early handling procedure, which resulted in increased maternal care, was able to counteract the detrimental effects induced by gestational corticosterone exposure both in the behavioral- and neurochemical parameters examined. These findings highlight the potentially detrimental consequences of targeting the stress system during pregnancy as a vulnerability factor for the occurrence of emotional and affective distress in the adolescent offspring. Maternal extra-care proves to be a protective strategy that confers resiliency and restores homeostasis.

How Early Life Stress Impact Maternal Care: A Systematic Review of Rodent Studies

Background: Maternal care refers to the behavior performed by the dam to nourish and protect her litter during its early development. Frequent and high-quality performance of such maternal behaviors is critical for the neurodevelopment of the pups. Maternal exposure to stress during early development can impair maternal care and amplify the deleterious effects of poor maternal caregiving and neglect. As such, a thorough understanding of the effects caused by several models of early life stress on maternal care may yield more insights into the relationship between stress and maternal behavior.

Methods: A systematic review was performed to identify and address the effects of early life stress on maternal behavior. The search was conducted using three online databases: PUBMED, Embase, and Web of Science. To provide clear evidence of the impact of stress on maternal care, in every study, the stress group was always compared to a control group. Outcomes were categorized into eight different behaviors: (1) licking/grooming; (2) arched-back nursing; (3) blanket-nursing/passive nursing; (4) nest building; (5) contact with pups; (6) harmful/adverse caregiving; (7) no contact; (8) nest exits. Additionally, the methodological quality of the studies was evaluated.

Results: A total of 12 different early life stress protocols were identified from the 56 studies included in this systematic review. Our data demonstrate that different stress models can promote specific maternal patterns of behavior. Regarding the maternal separation protocol, we observed an overall increase in nursing and licking/grooming behaviors, which are essential for pup development. An increase in the number of nest exits, which represents a fragmentation of maternal care, was observed in the limited bedding protocol, but the total amount of maternal care appears to remain similar between groups.

Conclusions: Each stress protocol has unique characteristics that increase the difficulty of rendering comparisons of maternal behavior. The increase in maternal care observed in the maternal separation protocol may be an attempt to overcompensate for the time off-nest. Fragmented maternal care is a key component of the limited bedding protocol. Moreover, the methodological approaches to evaluate maternal behavior, such as time, duration, and behavior type should be more homogeneous across studies.

Strain differences in maternal neuroendocrine and behavioral responses to stress and the relation to offspring cocaine responsiveness

Early life stress exposure, including prenatal stress (PNS), influences subsequent risk for many disorders, including substance abuse, and these effects interact with genetic factors to determine risk for disease. We previously demonstrated gene X environmental interactions across the BXD recombinant inbred mouse strain panel and their progenitor strains in PNS modulation of cocaine-induced reward and locomotion. Critical to dissecting genetic interactions with PNS is consideration of the modes of stress transmission to the offspring. Both maternal neuroendocrine responses during stress and subsequent maternal-offspring interactions following stress may serve as transmission modes for PNS-induced changes in cocaine responsiveness. Therefore, we characterized the maternal stress response by measuring restraint stress-induced plasma corticosterone (CORT) during gestation as well as effects of restraint stress on dam-pup contact in the first 10 postnatal days in BXD and progenitor mouse strains. Restraint stress interacted with strain to affect plasma CORT levels and dam-pup contact, indicating heritable variation of the maternal stress response. Furthermore, strain-level variance in maternal stress response correlated to the impact on cocaine response exhibited by adult offspring. These findings implicate multiple modes of maternal stress response in alterations of offspring drug responsiveness and indicate that assessment of maternal endocrine and behavioral responses during early life can be utilized to dissect the complex intersection of maternal factors, the response of the offspring and genetics.

Mothering under the influence: how perinatal drugs of abuse alter the mother-infant interaction

Although drug-abusing women try to moderate their drug and alcohol use during pregnancy, they often relapse at a time when childcare needs are high and maternal bonding is critical to an infant's development. In the clinical setting, the search for the neural basis of drug-induced caregiving deficits is complex due to several intervening variables. Rather, the preclinical studies that control for drug dose and regimen, as well as for gestational and postpartum environment, allow a precise determination of the effects of drugs on maternal behaviour. Given the relevance of the issue, this review will gather reports on the phenotypic correlates of maternal behaviour in preclinical studies, and focus on the detrimental consequences on the mother-infant interaction exerted by the perinatal use of alcohol, nicotine, cannabis, cocaine and stimulants and opiates. The drug-induced disruptions of this maternal repertoire are associated with adverse maternal and infant outcomes. A comprehensive overview will help promote the refinement of the treatment approaches toward maternal drug use disorders and maternal misbehaviour, in favour of augmented parenting resiliency.

High-Salt Exposure During Perinatal Development Enhances Stress Sensitivity

Excess consumption of dietary sodium during pregnancy has been shown to impair offspring cardiovascular function and enhance salt preference in adulthood, but little is known regarding the long-term impact of this nutritional surplus on offspring brain morphology and behavior. Using a combination of cellular and behavioral approaches, we examined the impact of maternal salt intake during the perinatal period on structural plasticity in the prefrontal cortex (PFC) and nucleus accumbens (NAc) in weanling and adult offspring as well as reward- and stress-driven behaviors in adult offspring. We found that weanling rats born to 4% NaCl-fed dams exhibited an increase and decrease in thin spine density in the infralimbic PFC (IL-PFC) and prelimbic PFC (PL-PFC), respectively, as well as an increase in mushroom spine density in the NAc shell, compared to 1% NaCl-fed controls. Structural changes in the IL-PFC and NAc shell persisted into adulthood, the latter of which is a phenotype that has been observed in rats exposed to early life stress. There was no effect of maternal salt intake on reward-driven behaviors, including sucrose preference, conditioned place preference (CPP) for cocaine, and forced swim stress (FSS)-induced reinstatement of cocaine-induced CPP. However, rats born to high-salt fed dams spent less time swimming in the FSS and displayed heightened plasma CORT levels in response to the FSS compared to controls, suggesting that early salt exposure increases stress sensitivity. Overall, our results suggest that perinatal salt exposure evokes lasting impacts on offspring physiology and behavior.

Prenatal stress effects in a wild, long-lived primate: predictive adaptive responses in an unpredictable environment

Prenatal maternal stress affects offspring phenotype in numerous species including humans, but it is debated whether these effects are evolutionarily adaptive. Relating stress to adverse conditions, current explanations invoke either short-term developmental constraints on offspring phenotype resulting in decelerated growth to avoid starvation, or long-term predictive adaptive responses (PARs) resulting in accelerated growth and reproduction in response to reduced life expectancies. Two PAR subtypes were proposed, acting either on predicted internal somatic states or predicted external environmental conditions, but because both affect phenotypes similarly, they are largely indistinguishable. Only external (not internal) PARs rely on high environmental stability particularly in long-lived species. We report on a crucial test case in a wild long-lived mammal, the Assamese macaque (Macaca assamensis), which evolved and lives in an unpredictable environment where external PARs are probably not advantageous. We quantified food availability, growth, motor skills, maternal caretaking style and maternal physiological stress from faecal glucocorticoid measures. Prenatal maternal stress was negatively correlated to prenatal food availability and led to accelerated offspring growth accompanied by decelerated motor skill acquisition and reduced immune function. These results support the ‘internal PAR’ theory, which stresses the role of stable adverse internal somatic states rather than stable external environments.

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.

Laboratory environmental factors and pain behavior: the relevance of unknown unknowns to reproducibility and translation

The poor record of basic-to-clinical translation in recent decades has led to speculation that preclinical research is "irreproducible", and this irreproducibility in turn has largely been attributed to deficiencies in reporting and statistical practices. There are, however, a number of other reasonable explanations of both poor translation and difficulties in one laboratory replicating the results of another. This article examines these explanations as they pertain to preclinical pain research. I submit that many instances of apparent irreproducibility are actually attributable to interactions between the phenomena and interventions under study and "latent" environmental factors affecting the rodent subjects. These environmental variables-often causing stress, and related to both animal husbandry and the specific testing context-differ greatly between labs, and continue to be identified, suggesting that our knowledge of their existence is far from complete. In pain research in particular, laboratory stressors can produce great variability of unpredictable direction, as stress is known to produce increases (stress-induced hyperalgesia) or decreases (stress-induced analgesia) in pain depending on its parameters. Much greater attention needs to be paid to the study of the laboratory environment if replication and translation are to be improved.

Effects of prenatal exposure to WIFI signal (2.45GHz) on postnatal development and behavior in rat: Influence of maternal restraint

The present study was carried out to investigate the potential combined influence of maternal restraint stress and 2.45GHz WiFi signal exposure on postnatal development and behavior in the offspring of exposed rats. 24 pregnant albino Wistar rats were randomly assigned to four groups: Control, WiFi-exposed, restrained and both WiFi-exposed and restrained groups. Each of WiFi exposure and restraint occurred 2h/day along gestation till parturition. The pups were evaluated for physical development and neuromotor maturation. Moreover, elevated plus maze test, open field activity and stationary beam test were also determined on postnatal days 28, 30 and 31, respectively. After behavioral tests, the rats were anesthetized and their brains were removed for biochemical analysis. Our main findings showed no detrimental effects on gestation progress and outcomes at delivery in all groups. Subsequently, WiFi and restraint, per se and mainly in concert altered physical development of pups with slight differences between genders. Behaviorally, the gestational WiFi irradiation, restraint and especially the associated treatment affected the neuromotor maturation mainly in male progeny. At adult age, we noticed anxiety, motor deficit and exploratory behavior impairment in male offspring co-exposed to WiFi radiation and restraint, and in female progeny subjected to three treatments. The biochemical investigation showed that, all three treatments produced global oxidative stress in brain of both sexes. As for serum biochemistry, phosphorus, magnesium, glucose, triglycerides and calcium levels were disrupted. Taken together, prenatal WiFi radiation and restraint, alone and combined, provoked several behavioral and biochemical impairments at both juvenile and adult age of the offspring.

Prenatal maternal bereavement and mortality in the first decades of life: a nationwide cohort study from Denmark and Sweden

BACKGROUND

The loss of a close relative is one of the most stressful life events. In pregnancy, this experience has been associated with a higher risk of fetal death and under-five mortality, but little is known about potential effects on long-term mortality in offspring. We examined the association between prenatal maternal bereavement and mortality in a cohort of 5.3 million children followed until up to 37 years of age.

METHOD

The population-based cohort study included 5 253 508 live singleton births in Denmark (1973-2004) and Sweden (1973-2006). Children born to mothers who lost a child, spouse, sibling, or parent during or 1 year before pregnancy were categorized as exposed.

RESULTS

Prenatal maternal bereavement was associated with a 10% increased all-cause mortality risk in offspring [mortality rate ratio (MRR) 1.10, 95% confidence interval (CI) 1.03-1.18]. The association was the most pronounced for children of mothers who lost a child/spouse (MRR 1.28, 95% CI 1.14-1.44) and was stronger during the first 10 years of life. Prenatal maternal bereavement may have stronger effects on natural causes of death in offspring, including infectious/parasitic disease (MRR 1.86, 95% CI 1.07-3.23), endocrine/nutritional/metabolic diseases (MRR 3.23, 95% CI 2.02-5.17), diseases of nervous system (MRR 3.36, 95% CI 2.47-4.58), and congenital malformations (MRR 1.39, 95% CI 1.08-1.80). No excess mortality risk in offspring was observed for unnatural causes of death.

CONCLUSION

Prenatal maternal bereavement was associated with an increased long-term mortality risk in offspring, particularly for selected natural causes of diseases and medical conditions. Our results support the fetal programming hypothesis that prenatal stress may contribute to ill health from physical diseases later in life.

The effects of prenatal "psychological" stressor exposure on lung inflammation and hyperresponsiveness in adult rat offspring

The aim of this study was to establish whether exposure of pregnant rats to uncontrollable (psychological) stressors might change the likelihood of their offspring to exhibit functional and histopathological abnormalities suggestive of asthma in adulthood. Pregnant rats (n = 16) underwent one of three treatments: electric shocks of a maximum duration of 10 s that could be escaped (controllable group; C) those that could not be escaped (uncontrollable group; U) or no shocks (control group; N). The offspring (n = 54) were kept in animal house under standard conditions until 3 months of age, when lung hyperresponsiveness, histopathology, immunohistochemical measurements of the cytokines interleukin (IL) 2, IL-4, IL-5, and IL-13 and actin as well as oxidative stress based on iNOS-positive cell counts and isoprostane PGF2α contents were assessed. The results showed that prenatal exposure to physical stressors (shocks) caused lung hyperresponsiveness and increased cytokine expression; exposure to uncontrollable shock (group U) had a differential effect on the expression of IL-2, IL-5, and IL-13 in inflammatory cells compared to exposure to controllable shock (group C), which characterizes the "psychological" aspect of stress. The results show that not only stress but also its uncontrollability during gestation might increase the likelihood that the offspring will exhibit functional and histopathological abnormalities suggestive of asthma. These findings strengthen the importance of psychological control with regard to environmental stimuli for the occurrence of several illnesses, suggesting the desirability of integration among various fields of science.

Biobehavioral consequences of prenatal exposure to a matrilineal overthrow and relocation in captive infant rhesus (Macaca mulatta) monkeys

There is a general consensus that perinatal experiences help to shape infant behavior; however, relatively little is known about the effects of prenatal experience on postnatal phenotype in non-human primates. The current study sought to take advantage of a naturally occurring incident in a captive population of rhesus monkeys. Following a matrilineal overthrow in an outdoor field cage, pregnant female rhesus macaques were relocated from outdoor to indoor housing. Using data collected from the California National Primate Research Center's Biobehavioral Assessment Program, we assessed infants born to mothers that were in their first or second trimester of pregnancy during the overthrow and relocation, and compared their data with that of animals from two control groups born in the same year: indoor mother raised infants and field cage reared infants. Our results suggest that the experience of an overthrow and relocation during the first trimester elevated postnatal emotional responsiveness, while the same experience in the second trimester resulted in modified HPA axis regulation, elevated glucocorticoid output following maternal separation, and lower hematocrit levels compared to control groups. These data add to a growing body of literature that prenatal experiences represent a significant contribution to postnatal phenotypic variability. Findings such as ours have implications for studies in captive management and the management of captive rhesus monkey populations. Am. J. Primatol. 78:895-903, 2016. © 2016 Wiley Periodicals, Inc.

Differential effects of prenatal stress on metabolic programming in diet-induced obese and dietary-resistant rats

Stress during pregnancy is a known contributing factor for the development of obesity in the offspring. Since maternal obesity is on the rise, we wanted to identify the effects of prenatal stress in the offspring of diet-induced obese (DIO) rats and compare them with the offspring of dietary-resistant (DR) rats. We hypothesized that prenatal stress would make both DIO and DR offspring susceptible to obesity, but the effect would be more pronounced in DIO rats. Pregnant DIO and DR rats were divided into two groups: nonstressed controls (control) and prenatal stress (subjected to restraint stress, three times/day from days 14 to 21 of gestation). After recording birth weight and weaning weight, male offspring were weaned onto a chow diet for 9 wk and shifted to a high-fat (HF) diet for 1 wk. At the end of the 10th wk the animals were euthanized, and visceral adipose mass, blood glucose, serum insulin, and C-peptide levels were measured. Prenatal stress resulted in hyperinsulinemia and higher C-peptide levels without altering caloric intake, body weight gain, or fat mass in the DIO offspring after 1 wk of HF intake, but not in DR offspring. To determine the mechanism underlying the hyperinsulinemia, we measured the levels of CEACAM1 that are responsible for insulin clearance. CEACAM1 levels in the liver were reduced in prenatally stressed DIO offspring after the HF challenge, suggesting that preexisting genetic predisposition in combination with prenatal stress increases the risk for obesity in adulthood, especially when offspring are fed a HF diet.

Mild effects of gestational stress and social reactivity on the onset of mother-young interactions and bonding in sheep

Consequences of prenatal stress on mother-young relationships are well-documented in altricial mammals but less so in precocial mammals. In this study, we investigated the effects of unpredictable aversive events on maternal behavior and mutual mother-young recognition in pregnant ewes while accounting for modulatory effects of ewe reactivity. From a population of 120 Romane-breed ewes, we selected 20 high-responsive (HR) and 20 low-responsive (LR) ewes according to pre-mating reactivity assessed in isolation tests. Over the final third of pregnancy, 10 HR ewes and 10 LR ewes were exposed daily to various aversive events such as social isolation, mixing and transport (stressed ewes), while the other 20 ewes were not exposed to aversive events (control ewes). Although the treatment induced chronic stress, physiologically confirmed by an increase in salivary cortisol following transport and sham shearing, maternal behavior of stressed ewes observed during the first 30 min postpartum and in the selectivity test 1 h 30 min later did not differ from controls. However, in a maternal motivation test performed 48 h postpartum, stressed ewes vocalized less than controls when separated from their lambs, and walked less readily past an unknown object to reach their lambs. Lambs of stressed ewes spent more time near their dam in a preference test performed 15 h after birth compared to control-ewe lambs. HR ewes spent more time grooming their lambs than LR ewes. We posit that domestication could have selected animals displaying robust expression of maternal behavior related to social reactivity and producing offspring that are better adapted to challenging situations.

Maternal care interacts with prenatal stress in altering sexual dimorphism in male rats

The present study analyzes the interaction between prenatal stress and mother's behavior on brain, hormonal, and behavioral development of male offspring in rats. It extends to males our previous findings, in females, that maternal care can alter behavioral dimorphism that becomes evident in the neonates when they mature. Experiment 1 compares the maternal behavior of foster mothers toward cross-fostered pups versus mothers rearing their own litters. Experiment 2 ascertains the induced "maternal" behavior of the male pups, derived from Experiment 1 when they reached maturity. The most striking effect was that the males non-exposed to the stress as fetuses and raised by stressed foster mothers showed the highest levels of "maternal" behavior of all the groups (i.e., induction of maternal behavior and retrieving behavior), not differing from the control, unstressed, female groups. Furthermore, those males showed significantly fewer olfactory bulb mitral cells than the control males that were non-stressed as fetuses and raised by their own non-stressed mothers. They also presented the lowest levels of plasma testosterone of all the male groups. The present findings provide evidence that prenatal environmental stress can "demasculinize" the behavior, brain anatomy and hormone secretion in the male fetuses expressed when they reach maturity. Moreover, the nature of the maternal care received by neonates can affect the behavior and physiology that they express at maturity.

Impact of combined prenatal ethanol and prenatal stress exposure on anxiety and hippocampal-sensitive learning in adult offspring

BACKGROUND

Prenatal ethanol (EtOH) and prenatal stress have both been independently shown to induce learning deficits and anxiety behavior in adult offspring. However, the interactive effects of these 2 developmental teratogens on behavioral outcomes have not been systematically evaluated.

METHODS

We combined an established moderate prenatal EtOH consumption paradigm where Long-Evans rat dams voluntarily consume either a 0 or 5% EtOH solution in 0.066% saccharin water (resulting in a mean peak maternal serum EtOH concentration of 84 mg/dl) with a novel prenatal stress paradigm. Pregnant rats were exposed to 3% 2,3,5-trimethyl-3-thiazoline (TMT) for 20 minutes a day on gestational days 13, 15, 17, and 19. Adult female offspring were evaluated for anxiety-like behavior using an elevated plus-maze and hippocampal-sensitive learning using a 2-trial trace conditioning (TTTC) task.

RESULTS

TMT exposure produced a threefold increase in maternal serum corticosterone compared to nonexposed, unhandled controls. Neither prenatal exposure paradigm, either alone or in combination, altered maternal weight gain, EtOH consumption, maternal care of litters, litter size, pup birth weight, or pup weight gain up to weaning. Offspring exposed to prenatal stress displayed significant increases in anxiety-like behavior in the elevated plus maze in terms of open arm entries and time spent on the open arms, with no significant effect of prenatal EtOH exposure and no interaction of the 2 prenatal exposures. Performance in a TTTC task revealed a significant effect of prenatal EtOH exposure on freezing behavior on the testing day, with no significant effect of prenatal stress exposure and no interaction of the 2 prenatal exposures.

CONCLUSIONS

While each prenatal exposure independently produced different behavioral outcomes, the results indicate that there is no significant interaction of prenatal EtOH and prenatal stress exposures on learning or anxiety at the exposure levels employed in this dual exposure paradigm. Subsequent studies will examine whether similar outcomes occur in male offspring and whether other measures of anxiety or learning are differentially impacted by these prenatal exposure paradigms.

Combination of prenatal immune challenge and restraint stress affects prepulse inhibition and dopaminergic/GABAergic markers

Gestational immune challenge with the viral-like antigen poly I:C is a well-established neurodevelopmental model of schizophrenia. However, exposure to inflammation during early life may sensitize the developing brain to secondary insults and enhance the central nervous system vulnerability. To gain a better understanding of the pathophysiology of schizophrenia, we thus developed a two-hit animal model based on prenatal poly I:C immune challenge followed by restraint stress in juvenile mice. C57BL/6 gestational mice were intraperitoneally injected with poly I:C or saline at gestational day 12. Pups were then submitted or not, to restraint stress for 2h, for three consecutive days, from postnatal days 33 to 35. Prepulse inhibition (PPI) of acoustic startle response is commonly used to assess sensorimotor gating, a neural process severely disrupted in patients with schizophrenia. Our results revealed that the combination of prenatal immune challenge with poly I:C followed by a restraint stress period was able to induce a PPI disruption in 36-day-old pups, as opposed to each insult applied separately. PPI deficits were accompanied by dopaminergic and GABAergic abnormalities in the prefrontal cortex and striatum. Indeed, measurements of cortical and striatal dopamine D2 receptor (D2R) mRNA and protein levels revealed that the combination of gestational exposure to poly I:C and postnatal restraint stress induced an increase in D2R protein and mRNA levels. Likewise, the combination of both insults reduced the mRNA and protein expression levels of the 67 kDa form of glutamic acid decarboxylase (GAD67), in those two brain regions. To our knowledge, this two-hit animal model is the first in vivo model reporting PPI deficits at pubertal age. This two-hit animal model may also help in studying innovative therapies dedicated to the treatment of schizophrenia, especially in its early phase.

Sex-specific effects of exercise ancestry on metabolic, morphological and gene expression phenotypes in multiple generations of mouse offspring

Early life and preconception environmental stimuli can affect adult health-related phenotypes. Exercise training is an environmental stimulus affecting many systems throughout the body and appears to alter offspring phenotypes. The aim of this study was to examine the influence of parental exercise training, or 'exercise ancestry', on morphological and metabolic phenotypes in two generations of mouse offspring. The F0 C57BL/6 mice were exposed to voluntary exercise (EX) or sedentary lifestyle (SED) and bred with like-exposed mates to produce an F1 generation. The F1 mice of both ancestries were sedentary and killed at 8 weeks or bred with littermates to produce an F2 generation, which was also sedentary and killed at 8 weeks. Small but broad generation- and sex-specific effects of exercise ancestry were observed for body mass, fat and muscle mass, serum insulin, glucose tolerance and muscle gene expression. The F1 EX females were lighter than F1 SED females and had lower absolute tibialis anterior and omental fat masses. Serum insulin was higher in F1 EX females compared with F1 SED females. The F2 EX females had impaired glucose tolerance compared with F2 SED females. Analysis of skeletal muscle mRNA levels revealed several generation- and sex-specific differences in mRNA levels for multiple genes, especially those related to metabolic genes (e.g. F1 EX males had lower mRNA levels of Hk2, Ppard, Ppargc1a, Adipoq and Scd1 than F1 SED males). These results provide preliminary evidence that parental exercise training can influence health-related phenotypes in mouse offspring.

Prenatal stress alters the behavior and dendritic morphology of the medial orbitofrontal cortex in mouse offspring during lactation

Several preclinical and clinical studies have shown that prenatal stress alters neuronal dendritic development in the prefrontal cortex, together with behavioral disturbances (anxiety). Nevertheless, neither whether these alterations are present during the lactation period, nor whether such findings may reflect the onset of anxiety disorders observed in childhood and adulthood has been studied. The central aim of the present study was to determine the effects of prenatal stress on the neuronal development and behavior of mice offspring during lactation (postnatal days 14 and 21). We studied 24 CF-1 male mice, grouped as follows: (i) control P14 (n=6), (ii) stressed P14 (n=6), (iii) control P21 (n=6) and (iv) stressed P21 (n=6). On the corresponding days, animals were evaluated with the open field test and sacrificed. Their brains were then stained in Golgi-Cox solution for 30 days. The morphological analysis dealt with the study of 96 pyramidal neurons. The results showed, first, that prenatal stress resulted in a significant (i) decrease in the apical dendritic length of pyramidal neurons in the orbitofrontal cortex at postnatal day 14, (ii) increase in the apical dendritic length of pyramidal neurons in the orbitofrontal cortex at postnatal day 21, and (iii) reduction in exploratory behavior at postnatal day 14 and 21.

Effects of chronic stress during pregnancy on maternal performance in the guinea pig (Cavia aperea f. porcellus)

Stress experienced during pregnancy can have persistent impact on the female's physiology and behaviour not only during but even beyond pregnancy. The present study aimed to evaluate such long-term effects of stress in terms of repeated strobe light exposure during early to mid gestation on behavioural aspects of mothering activities and lactational effort in lactating guinea pigs. We found that maternal behaviour was negatively affected by stress experience during pregnancy with treatment females developing a higher level of offspring-directed aggression than controls. In addition, our measure of lactational performances showed tendencies of lowered milk supply and longer pup suckling durations in stressed females. We suggest that this may represent a strategy to advance infant weaning following demanding conditions caused by chronic stress experience during pregnancy.

Luman/CREB3 recruitment factor regulates glucocorticoid receptor activity and is essential for prolactin-mediated maternal instinct

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system in animal responses to stress. It is known that the HPA axis is attenuated at parturition to prevent detrimental effects of glucocorticoid secretion including inhibition of lactation and maternal responsiveness. Luman/CREB3 recruitment factor (LRF) was identified as a negative regulator of CREB3 which is involved in the endoplasmic reticulum stress response. Here, we report a LRF gene knockout mouse line that has a severe maternal behavioral defect. LRF(-/-) females lacked the instinct to tend pups; 80% of their litters died within 24 h, while most pups survived if cross-fostered. Prolactin levels were significantly repressed in lactating LRF(-/-) dams, with glucocorticoid receptor (GR) signaling markedly augmented. In cell culture, LRF repressed transcriptional activity of GR and promoted its protein degradation. LRF was found to colocalize with the known GR repressor, RIP140/NRIP1, which inhibits the activity by GR within specific nuclear punctates that are similar to LRF nuclear bodies. Furthermore, administration of prolactin or the GR antagonist RU486 restored maternal responses in mutant females. We thus postulate that LRF plays a critical role in the attenuation of the HPA axis through repression of glucocorticoid stress signaling during parturition and the postpartum period.

Chronic cocaine exposure during pregnancy increases postpartum neuroendocrine stress responses

The cycle of chronic cocaine (CC) use and withdrawal results in increased anxiety, depression and disrupted stress-responsiveness. Oxytocin and corticosterone (CORT) interact to mediate hormonal stress responses and can be altered by cocaine use. These neuroendocrine signals play important regulatory roles in a variety of social behaviours, specifically during the postpartum period, and are sensitive to disruption by CC exposure in both clinical settings and preclinical models. To determine whether CC exposure during pregnancy affected behavioural and hormonal stress response in the early postpartum period in a rodent model, Sprague-Dawley rats were administered cocaine daily (30 mg/kg) throughout gestation (days 1-20). Open field test (OFT) and forced swim test (FST) behaviours were measured on postpartum day 5. Plasma CORT concentrations were measured before and after testing throughout the test day, whereas plasma and brain oxytocin concentrations were measured post-testing only. The results obtained indicated increased CORT response after the OFT in CC-treated dams (P ≤ 0.05). CC-treated dams also exhibited altered FST behaviour (P ≤ 0.05), suggesting abnormal stress responsiveness. Peripheral, but not central, oxytocin levels were increased by cocaine treatment (P ≤ 0.05). Peripheral oxytocin and CORT increased after the FST, regardless of treatment condition (P ≤ 0.05). Changes in stress-responsiveness, both behaviourally and hormonally, may underlie some deficits in maternal behaviour; thus, a clearer understanding of the effect of CC on the stress response system may potentially lead to treatment interventions that could be relevant to clinical populations. Additionally, these results indicate that CC treatment can have long-lasting effects on peripheral oxytocin regulation in rats, similar to changes observed in persistent social behaviour and stress-response deficits in clinical populations.

Chronic hypoxia exposure during pregnancy is associated with a decreased active nursing activity in mother and an abnormal birth weight and postnatal growth in offspring of rats

Stress during pregnancy is known to have a significant impact on animal's behavior and offspring development. The effects of gestational hypoxia on maternal behavior have not been studied. In the present study, we investigated the effects of gestational hypoxia exposure on dam's maternal behavior, offspring's growth and plasma corticosterone levels after parturition in rats. Altitude hypoxia (3 and 5 km) was simulated in the hypobaric chambers during the last week of pregnancy and the effects were compared to those found in controls exposed at sea level. We found that gestational hypoxia significantly decreased dam's arched-back nursing activity across the lactation period. The effect was more profound in 5 km group. Gestational hypoxia also altered other maternal behaviors such as blanket and passive nursing. Hypoxia exposure was associated with abnormal birth weight and postnatal growth in pups, with a significantly higher and lower birth weight than control found in 3 and 5 km groups, respectively, and accelerated growth in both stressed groups. Gestational hypoxia exposure significantly elevated plasma corticosterone levels in dams at the time of weaning and in pups across the measurement days. Taken together, the present results indicate that hypoxia, particularly severe hypoxia during the late phase of pregnancy has a significantly adverse impact on animal's behavior, endocrine function and offspring development. The higher birth weight found in the offspring of 3 km group suggests a compensatory system counteracting with the inhibitory effects of hypoxia on fetus growth at this altitude.

Both oxytocin and vasopressin are mediators of maternal care and aggression in rodents: from central release to sites of action

In the mammalian peripartum period, the activity of both the brain oxytocin and vasopressin system is elevated as part of the physiological adaptations occurring in the mother. This is reflected by increased expression and intracerebral release of oxytocin and vasopressin, as well as increased neuropeptide receptor expression and binding. In this review we discuss the functional role of the brain oxytocin and vasopressin system in the context of maternal behavior, specifically maternal care and maternal aggression in rodents. In order to enable the identification of significant and peptide-specific contributions to the display of maternal behavior, various complementary animal models of maternal care and/or maternal aggression were studied, including rats selectively bred for differences in anxiety-related behavior (HAB and LAB dams), monitoring of local neuropeptide release during ongoing maternal behavior, and local pharmacological or genetic manipulations of the neuropeptide systems. The medial preoptic area was identified as a major site for oxytocin- and vasopressin-mediated maternal care. Furthermore, both oxytocin and vasopressin release and receptor activation in the central amygdala and the bed nucleus of the stria terminalis play an important role for maternal aggression. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Prenatal stress produces sex differences in nest odor preference

Prenatal stress (PS) and early postnatal environment may alter maternal care. Infant rats learn to identify their mother through the association between maternal care and familiar odors. Female Wistar rats were exposed to restraint stress for 30 min, 4 sessions per day, in the last 7 days of pregnancy. At birth, pups were cross-fostered and assigned to the following groups: prenatal non-stressed mothers raising non-stressed pups (NS:NS), prenatal stressed mothers raising non-stressed pups (S:NS), prenatal non-stressed mothers raising stressed pups (NS:S), prenatal stressed mothers raising stressed pups (S:S). Maternal behaviors were assessed during 6 postpartum days. On postnatal day (PND) 7, the behavior of male and female pups was analyzed in the odor preference test; and noradrenaline (NA) activity in olfactory bulb (OB) was measured. The results showed that restraint stress increased plasma levels of corticosterone on gestational day 15. After parturition, PS reduced maternal care, decreasing licking the pups and increasing frequency outside the nest. Female pups from the NS:S, S:NS, S:S groups and male pups from the S:S group showed no nest odor preference. Thus, at day 7, female pups that were submitted to perinatal interventions showed more impairment in the nest odor preference test than male pups. No changes were detected in the NA activity in the OB. In conclusion, repeated restraint stress during the last week of gestation reduces maternal care and reduces preference for a familiar odor in rat pups in a sex-specific manner.

Differential effects of prenatal stress in 5-Htt deficient mice: towards molecular mechanisms of gene × environment interactions

Prenatal stress (PS) has been shown to influence the development of the fetal brain and to increase the risk for the development of psychiatric disorders in later life. Furthermore, the variation of human serotonin transporter (5-HTT, SLC6A4) gene was suggested to exert a modulating effect on the association between early life stress and the risk for depression. In the present study, we used a 5-Htt×PS paradigm to investigate whether the effects of PS are dependent on the 5-Htt genotype. For this purpose, the effects of PS on cognition, anxiety- and depression-related behavior were examined using a maternal restraint stress paradigm of PS in C57BL6 wild-type (WT) and heterozygous 5-Htt deficient (5-Htt +/-) mice. Additionally, in female offspring, a genome-wide hippocampal gene expression profiling was performed using the Affymetrix GeneChip® Mouse Genome 430 2.0 Array. 5-Htt +/- offspring showed enhanced memory performance and signs of reduced anxiety as compared to WT offspring. In contrast, exposure of 5-Htt +/- mice to PS was associated with increased depressive-like behavior, an effect that tended to be more pronounced in female offspring. Further, 5-Htt genotype, PS and their interaction differentially affected the expression of numerous genes and related pathways within the female hippocampus. Specifically, MAPK and neurotrophin signaling were regulated by both the 5-Htt +/- genotype and PS exposure, whereas cytokine and Wnt signaling were affected in a 5-Htt genotype×PS manner, indicating a gene×environment interaction at the molecular level. In conclusion, our data suggest that although the 5-Htt +/- genotype shows clear adaptive capacity, 5-Htt +/- mice--particularly females--at the same time appear to be more vulnerable to developmental stress exposure when compared to WT offspring. Moreover, hippocampal gene expression profiles suggest that distinct molecular mechanisms mediate the behavioral effects of the 5-Htt genotype, PS exposure, and their interaction.