Maternal glucocorticoid deficit affects hypothalamic-pituitary-adrenal function and behavior of rat offspring

Integrative Studies of the Effects of Mothers on Offspring: An Example from Wild North American Red Squirrels

Animal species vary in whether they provide parental care or the type of care provided, and this variation in parental care among species has been a common focus of comparative studies. However, the proximate causes and ultimate consequences of within-species variation in parental care have been less studied. Most studies about the impacts of within-species variation in parental care on parental fitness have been in primates, whereas studies in laboratory rodents have been invaluable for understanding what causes inter-individual variation in parental care and its influence on offspring characteristics. We integrated both of these perspectives in our long-term study of North American red squirrels (Tamiasciurus hudsonicus) in the Yukon, Canada, where we have focused on understanding the impacts of mothers on offspring. This includes documenting the impacts that mothers or the maternal environment itself has on their offspring, identifying how changes in maternal physiology impact offspring characteristics, the presence of individual variation in maternal attentiveness toward offspring before weaning and its fitness consequences, and postweaning maternal care and its fitness consequences. We provide an overview of these contributions to understanding the impacts mothers have on their offspring in red squirrels using an integrative framework and contrast them with studies in the laboratory.

Survival is negatively associated with glucocorticoids in a wild ungulate neonate

It is unknown how ungulate physiological responses to environmental perturbation influence overall population demographics. Moreover, neonatal physiological responses remain poorly studied despite the importance of neonatal survival to population growth. Glucocorticoid (GC) hormones potentially facilitate critical physiological and behavioral responses to environmental perturbations. However, elevated GC concentrations over time may compromise body condition and indirectly reduce survival. We evaluated baseline salivary cortisol (CORT; a primary GC in mammals) concentrations in 19 wild neonatal white-tailed deer (Odocoileus virginianus) in a northern (NS) and southern (SS) area in Pennsylvania. After ranking survival models consisting of variables hypothesized to influence neonate survival (i.e. weight, sex), the probability of neonate survival was best explained by CORT concentrations, where elevated CORT concentrations were associated with reduced survival probability to 12 weeks of age. Cortisol concentrations were greater in the SS where predation rates and predator densities were lower. As the first evaluation of baseline CORT concentrations in an ungulate neonate to our knowledge, this is also the first study to demonstrate CORT concentrations are negatively associated with ungulate survival at any life stage. Glucocorticoid hormones could provide a framework in which to better understand susceptibility to mortality in neonatal white-tailed deer.

Antenatal depression programs cortisol stress reactivity in offspring through increased maternal inflammation and cortisol in pregnancy: The Psychiatry Research and Motherhood - Depression (PRAM-D) Study

INTRODUCTION

Antenatal depression is associated with a broad range of suboptimal outcomes in offspring, although the underlying mechanisms are not yet understood. Animal studies propose inflammation and glucocorticoids as mediators of the developmental programming effect of prenatal stress on offspring stress responses, but studies in humans are not yet at this stage. Indeed, to date no single study has examined the effects of a rigorously defined, clinically significant Major Depressive Disorder (MDD) in pregnancy on maternal antenatal inflammatory biomarkers and hypothalamic-pituitary (HPA) axis, as well as on offspring HPA axis, behavior and developmental outcomes in the first postnatal year.

METHODS

A prospective longitudinal design was used in 106 women (49 cases vs. 57 healthy controls) to study the effect of MDD in pregnancy and associated antenatal biology (inflammatory and cortisol biomarkers), on offspring stress response (cortisol response to immunization, at 8 weeks and 12 months), early neurobehavior (Neonatal Behavioral Assessment Scale, NBAS, at day 6), and cognitive, language and motor development (Bayley Scales of Infant and Toddler Development at 12 months).

RESULTS

Compared with healthy controls, women with MDD in pregnancy had raised interleukin (IL) IL-6 (effect size (δ) = 0.53, p = 0.031), IL-10 (δ = 0.53, p = 0.043), tumor necrosis factor alpha (δ = 0.90, p = 0.003) and vascular endothelial growth factor (δ = 0.56, p = 0.008), together with raised diurnal cortisol secretion (δ = 0.89, p = 0.006), raised evening cortisol (δ = 0.64, p = 0.004), and blunted cortisol awakening response (δ = 0.70, p = 0.020), and an 8-day shorter length of gestation (δ = 0.70, p = 0.005). Furthermore, they had neonates with suboptimal neurobehavioral function in four out of five NBAS clusters measured (range of δ = 0.45-1.22 and p = 0.049-<0.001) and increased cortisol response to stress at one year of age (δ = 0.87, p < 0.001). Lastly, maternal inflammatory biomarkers and cortisol levels were correlated with infant stress response, suggesting a mechanistic link.

CONCLUSION

This study confirms and extends the notion that depression in pregnancy is associated with altered offspring behavior and biological stress response, and demonstrates that changes in maternal antenatal stress-related biology are associated with these infant outcomes.

Neuroanatomical pathways underlying the effects of hypothalamo-hypophysial-adrenal hormones on exploratory activity

When injected via the intracerebroventricular route, corticosterone-releasing hormone (CRH) reduced exploration in the elevated plus-maze, the center region of the open-field, and the large chamber in the defensive withdrawal test. The anxiogenic action of CRH in the elevated plus-maze also occurred when infused in the basolateral amygdala, ventral hippocampus, lateral septum, bed nucleus of the stria terminalis, nucleus accumbens, periaqueductal grey, and medial frontal cortex. The anxiogenic action of CRH in the defensive withdrawal test was reproduced when injected in the locus coeruleus, while the amygdala, hippocampus, lateral septum, nucleus accumbens, and lateral globus pallidus contribute to center zone exploration in the open-field. In addition to elevated plus-maze and open-field tests, the amygdala appears as a target region for CRH-mediated anxiety in the elevated T-maze. Thus, the amygdala is the principal brain region identified with these three tests, and further research must identify the neural circuits underlying this form of anxiety.

Impact of glucocorticoid on neurogenesis

Neurogenesis is currently an area of great interest in neuroscience. It is closely linked to brain diseases, including mental disorders and neurodevelopmental disease. Both embryonic and adult neurogeneses are influenced by glucocorticoids secreted from the adrenal glands in response to a variety of stressors. Moreover, proliferation/differentiation of the neural stem/progenitor cells (NSPCs) is affected by glucocorticoids through intracellular signaling pathways such as phosphoinositide 3-kinase (PI3K)/Akt, hedgehog, and Wnt. Our review presents recent evidence of the impact of glucocorticoids on NSPC behaviors and the underlying molecular mechanisms; this provides important information for understanding the pathological role of glucocorticoids on neurogenesis-associated brain diseases.

Maternal high-fat diet intensifies the metabolic response to stress in male rat offspring

BACKGROUND

The mother's consumption of high-fat food can affect glucose metabolism and the hypothalamic-pituitary-adrenal axis responsiveness in the offspring and potentially affect the metabolic responses to stress as well. This study examines the effect of maternal high-fat diet on the expression of pancreatic glucose transporter 2 and the secretion of insulin in response to stress in offspring.

METHODS

Female rats were randomly divided into normal and high-fat diet groups and were fed in accordance with their given diets from pre-pregnancy to the end of lactation. The offspring were divided into control (NC and HFC) and stress (NS and HFS) groups based on their mothers' diet and exposure to stress in adulthood. After the two-week stress induction period was over, an intraperitoneal glucose tolerance test (IPGTT) was performed and plasma glucose and insulin levels were assessed. The pancreas was then removed for measuring insulin secretion from the isolated islets as well as glucose transporter 2 mRNA expression and protein levels.

RESULTS

According to the results obtained, plasma corticosterone concentrations increased significantly on days 1 and 14 of the stress induction period and were lower on the last day compared to on the first day. In both the NS and HFS groups, stress reduced plasma insulin concentration in the IPGTT without changing the plasma glucose concentration, suggesting an increased insulin sensitivity in the NS and HFS groups, although more markedly in the latter. Stress reduced insulin secretion (at high glucose concentrations) and increased glucose transporter 2 mRNA and protein expression, especially in the HFS group.

CONCLUSION

Mothers' high-fat diet appears to intensify the stress response by changing the programming of the neuroendocrine system in the offspring.

Water deprivation increases maternal corticosterone levels and enhances offspring growth in the snake Vipera aspis

Circulating glucocorticoids (GCs) levels may increase as a result of reproductive effort or in response to unpredictable events. However, the GCs secretion can vary with the availability of vital trophic resources such as energy. While water represents another critical resource, the impact of water deprivation on GCs secretion during reproduction has not yet been thoroughly investigated. Here, we examined the effects of water deprivation on plasma corticosterone (CORT) concentrations of female aspic vipers (Vipera aspis), and we determined the impacts of water deprivation on offspring traits. We exposed both pregnant and non-reproductive females to a 20-day water deprivation and compared their pre- and post-deprivation CORT levels to those of control females. At the end of the treatment, only water-deprived pregnant females showed a significant increase in CORT levels. In pregnant females, changes in baseline CORT level were correlated to changes in female hydration state. Changes in baseline CORT levels were also negatively influenced by maternal reproductive effort in pregnant control females, while such relationship was not apparent in pregnant water-deprived females. Finally, we found that offspring from water-deprived females had higher growth rates than offspring from control females. Offspring growth was also positively correlated to changes in both maternal osmolality and baseline CORT levels. Together, our results suggest that dehydration increases maternal CORT levels which may subsequently influence offspring development. Further long-term field studies are therefore required to assess whether there is an adaptive significance of this response.

Transgenerational Transmission of Stress Pathology

Abstract. The impact of the environment early in life on long-term outcomes is well known. Stressful experiences during pre- and postnatal development can modulate the genetic programming of specific brain circuits underlying emotional and cognitive aspects of behavioral adaptation to stressful experiences later in life. Furthermore, there is documented evidence for gene-environment interactions in the context of early-life stress. Identical gene variants can be associated with different phenotypes depending on environmental factors. DNA methylation, an enzymatically-catalyzed modification of the DNA, is the mechanism through which phenotypes are regulated. The dynamics and plasticity of epigenetic mechanisms can have short-term, long-term, or transgenerational consequences. In epigenetic research, rodent models have targeted several behavioral and emotional phenotypes. These models have contributed significantly to our understanding of the environmental regulation of the developmental brain in early life. This review will highlight studies with rats and mice on epigenetic processes in fetal programming of stress-related mental disorders.

Role of the hypothalamic-pituitary-adrenal axis in developmental programming of health and disease

Adverse environments during the fetal and neonatal development period may permanently program physiology and metabolism, and lead to increased risk of diseases in later life. Programming of the hypothalamic-pituitary-adrenal (HPA) axis is one of the key mechanisms that contribute to altered metabolism and response to stress. Programming of the HPA axis often involves epigenetic modification of the glucocorticoid receptor (GR) gene promoter, which influences tissue-specific GR expression patterns and response to stimuli. This review summarizes the current state of research on the HPA axis and programming of health and disease in the adult, focusing on the epigenetic regulation of GR gene expression patterns in response to fetal and neonatal stress. Aberrant GR gene expression patterns in the developing brain may have a significant negative impact on protection of the immature brain against hypoxic-ischemic encephalopathy in the critical period of development during and immediately after birth.

Low heritabilities, but genetic and maternal correlations between red squirrel behaviours

Consistent individual differences in behaviour, and behavioural correlations within and across contexts, are referred to as animal personalities. These patterns of variation have been identified in many animal taxa and are likely to have important ecological and evolutionary consequences. Despite their importance, genetic and environmental sources of variation in personalities have rarely been characterized in wild populations. We used a Bayesian animal model approach to estimate genetic parameters for aggression, activity and docility in North American red squirrels (Tamiasciurus hudsonicus). We found support for low heritabilities (0.08-0.12), and cohort effects (0.07-0.09), as well as low to moderate maternal effects (0.07-0.15) and permanent environmental effects (0.08-0.16). Finally, we found evidence of a substantial positive genetic correlation (0.68) and maternal effects correlation (0.58) between activity and aggression providing evidence of genetically based behavioural correlations in red squirrels. These results provide evidence for the presence of heritable variation in red squirrel behaviour, but also emphasize the role of other sources of variation, including maternal effects, in shaping patterns of variation and covariation in behavioural traits.

Dexamethasone enhances oxidative stress-induced cell death in murine neural stem cells

Glucocorticoids (GCs) are essential for normal brain development; however, there is consistent evidence that prenatal exposure of the fetal brain to excess GCs permanently modifies the phenotype of neuronal cells. In this paper, the murine-derived multipotent stem cell line C17.2 was used, as an in vitro model, to investigate the impact of GCs on neural stem cell survival. Our results indicate that dexamethasone (Dex) increases the sensitivity of murine neural stem cells (NSCs) to 2,3-methoxy-1,4-naphthoquinone-induced apoptosis, and this effect could be blocked by the glucocorticoid-receptor (GR) antagonist mifepristone, strongly suggesting the involvement of the GR. Furthermore, our results show that Dex decreases cell number and induces a G1-arrest. We hypothesized that the mitochondria are the main target of Dex. Interestingly, after treatment with Dex, 72% of the investigated genes involved in the mitochondrial respiratory chain are down-regulated, as well as 29% of the genes encoding for antioxidant enzymes. In conclusion, using the C17.2 cell line as a model to study developmental neurotoxicity in vitro, we have shown that GCs can increase cellular sensitivity to oxidative stress and alter the phenotype of NCSs.

Variations in maternal care alter corticosterone and 17beta-estradiol levels, estrous cycle and folliculogenesis and stimulate the expression of estrogen receptors alpha and beta in the ovaries of UCh rats

BACKGROUND

Variations in maternal care are associated with neonatal stress, hormonal disturbances and reproductive injuries during adulthood. However, the effects of these variations on sex hormones and steroid receptors during ovary development remain undetermined. This study aimed to investigate whether variations in maternal care are able to influence the hormonal profile, follicular dynamics and expression of AR, ER-alpha and ER-beta in the ovaries of UCh rat offspring.

METHODS

Twenty-four adult UCh rats, aged 120 days, were randomly divided into two groups (UChA and UChB) and mated. Maternal care was assessed from birth (day 0) to the 10th postnatal day (PND). In adulthood, twenty adult female rats (UChA and UChB offspring; n = 10/group), aged 120 days, were euthanized by decapitation during the morning estrus.

RESULTS

UChA females (providing high maternal care) more frequently displayed the behaviors of carrying pups, as well as licking/grooming and arched back nursing cares. Also, mothers providing high care had elevated corticosterone levels. Additionally, offspring receiving low maternal care showed the highest estrous cycle duration, increased corticosterone and 17beta-estradiol levels, overexpression of receptors ER-alpha and ER-beta, increased numbers of primordial, antral and mature follicles and accentuated granulosa cell proliferation.

CONCLUSIONS

Our study suggests that low maternal care alters corticosterone and 17beta-estradiol levels, disrupting the estrous cycle and folliculogenesis and differentially regulating the expression of ER-alpha and ER-beta in the ovaries of adult rats.

Gestational and postpartum corticosterone exposure to the dam affects behavioral and endocrine outcome of the offspring in a sexually-dimorphic manner

Exposure to high levels of glucocorticoids in utero and during the postpartum period has a detrimental effect on brain development. We created an animal model of postpartum stress/depression based on administering high levels of corticosterone (CORT) to the dams during the postpartum period which caused behavioral changes and reduced hippocampal cell proliferation in the offspring. As the consequences of early exposure to glucocorticoids may depend on the dose and the developmental stage of the offspring, the present study was conducted to investigate the effects of low (10 mg/kg) or high levels of CORT (40 mg/kg) given to dams either during gestation, postpartum or across both gestation and postpartum on the outcome of the offspring. Male and female offspring were weighed throughout the experiment, tested in a series of behavioral tests (forced swim test, open field, elevated plus maze) and basal and restraint stress CORT levels were examined in adolescence or young adulthood. Results show that maternal CORT exposure, regardless of when administered, significantly attenuated body weight gain until adulthood in the offspring. Offspring exposed to low maternal CORT, but not high maternal CORT, during the postpartum had higher basal levels of CORT as young adults. Further, male and female offspring of dams exposed to high maternal CORT in utero showed more depressive-like behavior in the forced swim test, while males of dams exposed to high maternal CORT postpartum exhibited more anxiety-like behavior in the elevated plus maze. Taken together, maternal glucocorticoid exposure have long lasting effects on male and female offspring's behavioral and neuroendocrine measures in adolescence and adulthood depending on the time of exposure to glucocorticoids. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Neuroendocrine control of maternal stress responses and fetal programming by stress in pregnancy

The major changes in highly dynamic neuroendocrine systems that are essential for establishing and maintaining pregnancy are outlined from studies on rodents. These changes optimise the internal environment to provide the life support system for the placenta, embryo and fetus. These include automatic prevention of further pregnancy, blood volume expansion, increased appetite and energy storage. The brain regulates these changes, in response to steroid (estrogens, progesterone) and peptide (lactogens, relaxin) hormone signals. Activation of inhibitory endogenous opioid mechanisms in the brain in late pregnancy restrains premature secretion of oxytocin, and attenuates hypothalamo-pituitary-adrenal (HPA) responses to stress. This opioid mechanism is activated by allopregnanolone, a neuroactive progesterone metabolite. The significance of reduced HPA axis responses in shifting maternal metabolic balance, and in protecting the fetuses from adverse programming of HPA axis stress responsiveness and anxious behaviour in later life is critically discussed. Experimental studies showing sex-dependent fetal programming by maternal stress or glucocorticoid exposure in late pregnancy are reviewed. The possibility of over-writing programming in offspring through neurosteroid administration is discussed. The impact of maternal stress on placental function is considered in the context of reconciling studies that show offspring programming by stress in very early or late pregnancy produce similar phenotypes in the offspring.

"Green odor" inhalation by stressed rat dams reduces behavioral and neuroendocrine signs of prenatal stress in the offspring

Chronic maternal stress during pregnancy results in the "prenatally stressed" offspring displaying behavioral and neuroendocrine alterations that persist into adulthood. We investigated how inhalation of green odor (a mixture of equal amounts of trans-2-hexenal and cis-3-hexenol) by stressed dams might alter certain indices of prenatal stress in their offspring. These indices were depression-like behavior (increased immobility time in the forced-swim test) and acute restraint stress-induced changes in hypothalamo-pituitary-adrenocortical (HPA) axis activity [plasma corticosterone (CORT) and ACTH levels and the number of Fos-immunoreactive cells in the hypothalamic paraventricular nucleus (an index of neuronal activity)]. Pregnant rats were exposed to restraint stress for 60 min/day for 10 days (gestational days 10-19). The prenatally stressed offspring exhibited significant increases in depression-like behavior and in restraint stress-induced ACTH, CORT, and Fos responses, unless their dam had been exposed to green odor. The behavioral effect of the odor was also seen in offspring that were fostered by unstressed dams. The results obtained in the dams themselves were as follows. In vehicle-exposed stressed dams, but not in green odor-exposed ones, total body and adrenal weights were significantly decreased or increased, respectively. Depression-like behavior was not observed in the vehicle-exposed stressed dams themselves. Green odor inhalation prevented the impairment of maternal behavior induced by restraint stress. Thus, exposure of dams to stress may affect both the fetal brain and fetal HPA axis, and also maternal behavior, leading to altered behavioral and neuroendocrine responses in the offspring. Such effects may be prevented by the stressed dams inhaling green odor.

Depression during pregnancy and postpartum: contribution of stress and ovarian hormones

Depression is the most common psychiatric disease among women, exhibiting a prevalence which is 2-3x higher than in men. The postpartum period is considered the time of greatest risk for women to develop major depression and postpartum depression affects approximately 15% of women. A dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis is the most prominent endocrine change seen in depression and normalization of the HPA axis is a major target of recent therapies. Females exhibit different stress sensitivities than males which might contribute to their increased vulnerability for depression. Maternal stress or depression during pregnancy and/or postpartum is particularly concerning as early developmental influences can affect the maturation of the offspring as well as the mental health of the mother. Despite the urgent need for more information on depression in females, especially during pregnancy and postpartum, most animal models of depression have utilized only males. Given the sex differences in incidence of depression and treatment, it is vitally important to create or validate animal models of depression in females. This review will focus on the association between stress, glucocorticoids and depression in humans, with a special focus on depression in women during pregnancy and postpartum and on animal models of postpartum depression and the consequences for the offspring.

Prenatal alcohol exposure: fetal programming and later life vulnerability to stress, depression and anxiety disorders

Children with fetal alcohol spectrum disorder (FASD) exhibit cognitive, neuropsychological and behavioral problems, and numerous secondary disabilities including depression and anxiety disorders. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is common in depression/anxiety, reflected primarily in increased HPA tone or activity. Prenatal alcohol exposure (PAE) increases HPA tone and results in HPA dysregulation throughout life, paralleling many of the HPA changes in depression/anxiety. We review data demonstrating altered HPA function and increased depression/anxiety in FASD. In the context of the stress-diathesis model, we discuss the hypothesis that fetal programming of the HPA axis by PAE alters neuroadaptive mechanisms that mediate the stress response, thus sensitizing the organism to stressors encountered later in life, and mediating, at least partly, the increased vulnerability to depression/anxiety disorders. Furthermore, we present evidence demonstrating sex-specific alterations in both hormonal and behavioral responsiveness to tasks measuring depressive- and anxiety-like behaviors in PAE offspring. Overall, the research suggests that the stress-diathesis model provides a powerful approach for elucidating mechanisms underlying the increased vulnerability to mental illness among individuals with FASD, and developing appropriate treatments for these individuals. Dr. Seymour Levine's seminal work on the long-term consequences of early life experiences formed a framework for the development of the research described in this review.

Prenatal alcohol exposure and chronic mild stress differentially alter depressive- and anxiety-like behaviors in male and female offspring

BACKGROUND

Fetal Alcohol Spectrum Disorder (FASD) is associated with numerous neurobehavioral alterations, as well as disabilities in a number of domains, including a high incidence of depression and anxiety disorders. Prenatal alcohol exposure (PAE) also alters hypothalamic-pituitary-adrenal (HPA) function, resulting in increased responsiveness to stressors and HPA dysregulation in adulthood. Interestingly, data suggest that pre-existing HPA abnormalities may be a major contributory factor to some forms of depression, particularly when an individual is exposed to stressors later in life. We tested the hypothesis that exposure to stressors in adulthood may unmask an increased vulnerability to depressive- and anxiety-like behaviors in PAE animals.

METHODS

Male and female offspring from prenatal alcohol (PAE), pair-fed (PF), and ad libitum-fed control (C) treatment groups were tested in adulthood. Animals were exposed to 10 consecutive days of chronic mild stress (CMS), and assessed in a battery of well-validated tasks sensitive to differences in depressive- and/or anxiety-like behaviors.

RESULTS

We report here that the combination of PAE and CMS in adulthood increases depressive- and anxiety-like behaviors in a sexually dimorphic manner. PAE males showed impaired hedonic responsivity (sucrose contrast test), locomotor hyperactivity (open field), and alterations in affiliative and nonaffiliative social behaviors (social interaction test) compared to control males. By contrast, PAE and, to a lesser extent, PF, females showed greater levels of "behavioral despair" in the forced swim test, and PAE females showed altered behavior in the final 5 minutes of the social interaction test compared to control females.

CONCLUSIONS

These data support the possibility that stress may be a mediating or contributing factor in the psychopathologies reported in FASD populations.

Maternal isobutyl-paraben exposure decreases the plasma corticosterone level in dams and sensitivity to estrogen in female offspring rats

Isobutyl-paraben (IBP), a widely used preservative in a variety of foods, shows high comparative binding affinity to estrogen receptors. Here, we examined the effects of maternal exposure of rats to IBP on plasma hormone concentrations and organ weights in dams, ratio of male pups, anogenital distance, organ weights and plasma hormone concentrations in offspring, puberty, estrous cycle and response of organ weight and plasma hormone concentrations to estrogen in adult female offspring, and reproductive and adrenal function in adult male offspring, all of which are under developmental estrogen regulation, to clarify the estrogenic effects of IBP during gestation and lactation on the endocrine systems of dams and offspring. While maternal exposure of IBP decreased the plasma corticosterone concentration and increased the uterus weight in dams and increased uterine sensitivity to estrogen in adult female offspring, the other indices examined were largely unaffected by the present treatment. Even though these results indicate little sign of endocrine disrupting effects for IBP, the existence of activity may be a matter of concern due to the possible impact on the health of future generations.

Long-term postpartum anxiety and depression-like behavior in mother rats subjected to maternal separation are ameliorated by palatable high fat diet

While the effects of maternal separation on pups are well studied, the impact on dams has attracted little attention. The consumption of palatable food is known to dampen stress responses in animals, and emotions influence food choice in humans. Here we examined the early- and long-term impacts of maternal separation on behavioral profile of the dams, and the effects of palatable cafeteria high-fat diet (HFD). After littering, Sprague-Dawley female rats were subjected to prolonged separation, S180 (180 min) or brief separation, S15 (15 min/day) from postnatal days (PND) 2-14. At 4 weeks postpartum, half the dams were assigned to HFD. Anxiety and depression-like behaviors were assessed pre- and post-diet. Compared to S15 dams, S180 dams consuming chow demonstrated increased anxiety and depression-like behaviors assessed by elevated plus maze (EPM) and forced swim (FST) tests, respectively. These behavioral deficits were observed at 4 weeks, and persisted until 17 weeks postpartum. The S180 dams also had increased plasma corticosterone concentration compared to S15 dams, which coincided with increased hypothalamic CRH mRNA and reduced hippocampal GR mRNA expression, suggesting possible dysregulation of hypothalamic-pituitary-adrenal axis activity. Interestingly, continuous provision of HFD improved the behavioral deficits observed in S180 dams with significant reduction of hypothalamic CRH mRNA expression. These data are the first to describe long-term detrimental behavioral impacts of separation in dams, suggesting this may provide a model of postpartum depression. Moreover, they support the notion of long-term beneficial effects of 'comfort food' on stress responses.

High vitamin intake by Wistar rats during pregnancy alters tissue fatty acid concentration in the offspring fed an obesogenic diet

Diet during pregnancy affects the long-term health of the offspring. Vitamins are known to modulate lipid metabolism, which may be reflected in tissue fatty acid (FA) concentrations. The objective of this study was to investigate the effect of high vitamin intake during pregnancy on tissue FA concentration of the offspring. Wistar rats were fed an AIN-93G diet with either the recommended vitamin or 10-fold higher amounts (HV) during pregnancy. Afterward, offspring were weaned onto an obesogenic diet. Liver, quadriceps, adipose, and brain were collected over 48 weeks. Fatty acid concentration of tissue total lipids was analyzed by gas chromatography. At birth, the liver from HV offspring was higher in monounsaturated, stearic, and arachidonic acids. At weaning, the liver from HV offspring was higher in stearic and oleic acids; and in adipose tissue, n-6 and n-3 FAs were lower only in the male HV offspring (P < .05). At 12 weeks, HV offspring had higher concentrations of total fat, saturates, monounsaturates, and n-6 FA in muscle (P < .05), but not in other tissues. At 48 weeks, gestational diet did not affect tissue total lipid FA concentrations; but differences remained in specific tissue phospholipids species. Liver phospholipids from HV offspring were lower in monounsaturates and n-6 FA. Brain phosphatidylethanolamine was higher in oleic, n-6 FA, and docosahexaenoic acid in the HV offspring. Phosphatidylinositol was lower in saturates, monounsaturates, arachidonic, and docosahexaenoic acids only in HV female offspring. These observations demonstrate that high vitamin intake during pregnancy has short- and long-term effects on tissue FA concentration in the offspring.

Effects of maternal corticosterone and stress on behavioral and hormonal indices of formalin pain in male and female offspring of different ages

In previous studies, we showed for the first time that prenatal stress in rats produces long-term alterations of formalin-induced pain behavior that are dependent on age and sex, and we demonstrated an important role of the serotonergic system in mechanisms of prenatal stress (Butkevich, I.P. and Vershinina, E.A., 2001; Butkevich, I.P. and Vershinina, E.A., 2003; Butkevich, I.P., Mikhailenko, V.A., Vershinina, E.A., Khozhai, L.I., Grigorev, I.P., Otellin, V.A., 2005; Butkevich, I.P., Mikhailenko, V.A., Khozhai, L.I., Otellin, V.A., 2006). In the present study, we focus on the influence of the maternal corticosterone milieu and its role in the effects of stress during pregnancy on formalin-induced pain and the corticosterone response to it in male and female offspring of different ages. For this purpose, we used adrenalectomy (AD) in female rats 3-4 weeks before mating (as distinct from AD typically performed at the beginning of pregnancy). Since AD is considered a reliable method to treat hypercortisolism, researches on the effects of long-term AD in dams on the systems responsible for adaptive behavior in offspring are important (such studies are not described in the literature). The results demonstrate that the differences in the corticosterone response to injection of formalin and saline are obvious in 90-day-old (adult) female offspring but masked in 25-day-old ones. AD promoted the corticosterone response to formalin-induced pain but not to injection of saline in prenatally non-stressed female offspring of both ages. Prenatal stress canceled the differences in corticosterone response to injection of formalin and saline in 25-day-old offspring of AD dams and in adult offspring of sham-operated (SH) dams but caused similar differences in adult offspring of AD dams. Sex differences were found in basal corticosterone levels in AD prenatally stressed rats of both age groups, with a higher level in females, and in the corticosterone response to formalin-induced pain in the adult rats of all groups investigated, with higher corticosterone levels in females. In regard to pain behavior, AD induced significant changes in flexing+shaking in prenatally non-stressed adult offspring and canceled the differences in this behavior between non-stressed and stressed 25-day-old offspring. There were sex differences in pain behavior of the adult rats: greater flexing+shaking in AD non-stressed males but in SH non-stressed females; greater licking in prenatally-stressed AD and SH females. These results indicate that the long-term influences of maternal corticosterone on formalin-induced pain and the corticosterone response to it are determined by the sex and age of the offspring and suggest that other mechanisms, including serotonergic ones revealed in our previous studies, are involved in the effects of prenatal stress on inflammatory pain behavior.

Effects of prenatal dexamethasone treatment on physical growth, pituitary-adrenal hormones, and performance of motor, motivational, and cognitive tasks in juvenile and adolescent common marmoset monkeys

Synthetic glucocorticoids such as dexamethasone (DEX) are commonly used to prevent respiratory distress syndrome in preterm infants, but there is emerging evidence of subsequent neurobehavioral abnormalities (e.g. problems with inattention/hyperactivity). In the present study, we exposed pregnant common marmosets (Callithrix jacchus, primates) to daily repeated DEX (5 mg/kg by mouth) during either early (d 42-48) or late (d 90-96) pregnancy (gestation period of 144 days). Relative to control, and with a longitudinal design, we investigated DEX effects in offspring in terms of physical growth, plasma ACTH and cortisol titers, social and maintenance behaviors, skilled motor reaching, motivation for palatable reward, and learning between infancy and adolescence. Early DEX resulted in reduced sociability in infants and increased motivation for palatable reward in adolescents. Late DEX resulted in a mild transient increase in knee-heel length in infants and enhanced reversal learning of stimulus-reward association in adolescents. There was no effect of either early or late DEX on basal plasma ACTH or cortisol titers. Both treatments resulted in impaired skilled motor reaching in juveniles, which attenuated in early DEX but persisted in late DEX across test sessions. The increased palatable-reward motivation and decreased social motivation observed in early DEX subjects provide experimental support for the clinical reports that prenatal glucocorticoid treatment impairs social development and predisposes to metabolic syndrome. These novel primate findings indicate that fetal glucocorticoid overexposure can lead to abnormal development of motor, affective, and cognitive behaviors. Importantly, the outcome is highly dependent upon the timing of glucocorticoid overexposure.

Evaluation of developmental neurotoxicity: some important issues focused on neurobehavioral development

Exposure of the developing organism to industrial chemicals and physical factors represents a serious risk factor for the development of neurobehavioral disorders, such as attention-deficit hyperactivity disorder, autism and mental retardation. Appropriate animal models are needed to test potentially harmful effects and mechanisms of developmental neurotoxicity of various chemical substances. However, there are significant human vs. rat differences in the brain developmental profile which should be taken into account in neurotoxicity studies. Subtle behavioral alterations are hard to detect by traditional developmental toxicity and teratogenicity studies, and in many cases they remain hidden. They can however be revealed by using special behavioral, endocrine and/or pharmacological challenges, such as repeated behavioral testing, exposure to single stressful stimulus or drugs. Further, current neurobehavioral test protocols recommend to test animals up to their adulthood. However some behavioral alterations, such as anxiety-like behavior or mental deficiency, may become manifest in later periods of development. Our experimental and scientific experiences are highly suggestive for a complex approach in testing potential developmental neurotoxicity. Strong emphasis should be given on repeated behavioral testing of animals up to senescence and on using proper pharmacological and/or stressful challenges.

Psychological prenatal stress reduced the number of BrdU immunopositive cells in the dorsal hippocampus without affecting the open field behavior of male and female rats at one month of age

We examined whether prenatal psychological stress with little physical stress causes changes in the behavior and neurogenesis of the offspring of Sprague-Dawley rats at one month. Dams in the last trimester of gestation were psychologically stressed by placing them in a social communication box and shocking a rat on the other side of a transparent wall. They suffered little physical stress. Male and female offspring from the dams showed little change in an open field test at postnatal day (PND) 30. To evaluate neurogenesis in the brain, BrdU was intraperitoneally injected at PND 35 into offspring not used in the open field test. Immunohistochemical examinations of BrdU in their dorsal hippocampus at PNDs 42 and 112 revealed that the number of BrdU immunopositive cells in the offspring of prenatally stressed rats was significantly smaller than in the offspring of unstressed ones. These results together with our previous finding that prenatal psychological stress can alter specific behaviors suggest that prenatal psychological stress can suppress neurogenesis in the dorsal hippocampus of rats of both sexes at PND 35 even though impairment in the behavioral task has not yet appeared.

The long-term behavioural consequences of prenatal stress

Maternal distress during pregnancy increases plasma levels of cortisol and corticotrophin releasing hormone in the mother and foetus. These may contribute to insulin resistance and behaviour disorders in their offspring that include attention and learning deficits, generalized anxiety and depression. The changes in behaviour, with or independent of alterations in the function of the hypothalamic pituitary adrenal (HPA) axis, can be induced by prenatal stress in laboratory rodents and non-human primates. The appearance of such changes depends on the timing of the maternal stress, its intensity and duration, gender of the offspring and is associated with structural changes in the hippocampus, frontal cortex, amygdala and nucleus accumbens. The dysregulation of the HPA axis and behaviour changes can be prevented by maternal adrenalectomy. However, only the increased anxiety and alterations in HPA axis are re-instated by maternal injection of corticosterone.

CONCLUSION

Excess circulating maternal stress hormones alter the programming of foetal neurons, and together with genetic factors, the postnatal environment and quality of maternal attention, determine the behaviour of the offspring.