Sex differences in prenatally programmed anxiety behaviour in rats: differential corticotropin-releasing hormone receptor mRNA expression in the amygdaloid complex

Assessment of Prenatal Transportation Stress and Sex on Gene Expression Within the Amygdala of Brahman Calves

As the amygdala is associated with fear and anxiety, it is important to determine the potential effects of gestational stressors on behavior and stress responses in offspring. The objective of this study was to investigate the effects of prenatal transportation stress on amygdala gene expression in 25-day-old Brahman calves, focusing on sex-specific differences. Amygdala tissue samples from prenatally stressed (PNS) and control bull and heifer calves were analyzed using RNA sequencing. A thorough outlier detection process, utilizing visual inspection of multidimensional scaling plots, robust principal component analysis, and PCAGrid methods, led to the exclusion of 5 of 32 samples from subsequent analyses. Differential expression analysis revealed no significant treatment differences between the control and PNS groups within either sex. However, sex-specific differences in gene expression were identified in both the control and PNS groups. The control group showed seven differentially expressed genes between sexes, while ten were identified between PNS males and females, with seven located on the X chromosome. Among these was the ubiquitin-specific peptidase 9 X-linked gene, which plays a role in neurodevelopmental pathways. When comparing males to females, regardless of treatment, a total of 58 genes were differentially expressed, with 45 showing increased expression in females. Gene enrichment analysis indicated that many differentially expressed genes are associated with infectious disease-related pathways. Future research should explore amygdala size and functional responses to various postnatal stimuli.

CRF binding protein activity in the hypothalamic paraventricular nucleus is essential for stress adaptations and normal maternal behaviour in lactating rats

To ensure the unrestricted expression of maternal behaviour peripartum, activity of the corticotropin-releasing factor (CRF) system needs to be minimised. CRF binding protein (CRF-BP) might be crucial for this adaptation, as its primary function is to sequester freely available CRF and urocortin1, thereby dampening CRF receptor (CRF-R) signalling. So far, the role of CRF-BP in the maternal brain has barely been studied, and a potential role in curtailing activation of the stress axis is unknown. We studied gene expression for CRF-BP and both CRF-R within the paraventricular nucleus (PVN) of the hypothalamus. In lactating rats, Crh-bp expression in the parvocellular PVN was significantly higher and Crh-r1 expression in the PVN significantly lower compared to virgin rats. Acute CRF-BP inhibition in the PVN with infusion of CRF(6-33) increased basal plasma corticosterone concentrations under unstressed conditions in dams. Furthermore, while acute intra-PVN infusion of CRF increased corticosterone secretion in virgin rats, it was ineffective in vehicle (VEH)-pre-treated lactating rats, probably due to a buffering effect of CRF-BP. Indeed, pre-treatment with CRF(6-33) reinstated a corticosterone response to CRF in lactating rats, highlighting the critical role of CRF-BP in maintaining attenuated stress reactivity in lactation. To our knowledge, this is the first study linking hypothalamic CRF-BP activity to hypothalamic-pituitary-adrenal axis regulation in lactation. In terms of behaviour, acute CRF-BP inhibition in the PVN under non-stress conditions reduced blanket nursing 60 min and licking/grooming 90 min after infusion compared to VEH-treated rats, while increasing maternal aggression towards an intruder. Lastly, chronic intra-PVN inhibition of CRF-BP strongly reduced maternal aggression, with modest effects on maternal motivation and care. Taken together, intact activity of the CRF-BP in the PVN during the postpartum period is essential for the dampened responsiveness of the stress axis, as well as for the full expression of appropriate maternal behaviour.

How is prenatal stress transmitted from the mother to the fetus?

Prenatal stress programmes long-lasting neuroendocrine and behavioural changes in the offspring. Often this programming is maladaptive and sex specific. For example, using a rat model of maternal social stress in late pregnancy, we have demonstrated that adult prenatally stressed male, but not prenatally stressed female offspring display heightened anxiety-like behaviour, whereas both sexes show hyperactive hypothalamo-pituitary-adrenal (HPA) axis responses to stress. Here, we review the current knowledge of the mechanisms underpinning dysregulated HPA axis responses, including evidence supporting a role for reduced neurosteroid-mediated GABAergic inhibitory signalling in the brains of prenatally stressed offspring. How maternal psychosocial stress is signalled from the mother to the fetuses is unclear. Direct transfer of maternal glucocorticoids to the fetuses is often considered to mediate the programming effects of maternal stress on the offspring. However, protective mechanisms including attenuated maternal stress responses and placental 11β-hydroxysteroid dehydrogenase-2 (which inactivates glucocorticoids) should limit materno-fetal glucocorticoid transfer during pregnancy. Moreover, a lack of correlation between maternal stress, circulating maternal glucocorticoid levels and circulating fetal glucocorticoid levels is reported in several studies and across different species. Therefore, here we interrogate the evidence for a role for maternal glucocorticoids in mediating the effects of maternal stress on the offspring and consider the evidence for alternative mechanisms, including an indirect role for glucocorticoids and the contribution of changes in the placenta in signalling the stress status of the mother to the fetus.

The exploration of neuroinflammatory mechanism by which CRHR2 deficiency induced anxiety disorder

Inflammation stimulates the hypothalamic-pituitary adrenal (HPA) axis and triggers glial neuroinflammatory phenotypes, which reduces monoamine neurotransmitters by activating indoleamine 2,3-dioxygenase enzyme. These changes can induce psychiatric diseases, including anxiety. Corticotropin releasing hormone receptor 2 (CRHR2) in the HPA axis is involved in the etiology of anxiety. Omega(n)-3 polyunsaturated fatty acids (PUFAs) can attenuate anxiety through anti-inflammation and HPA axis modulation. However, the underlying molecular mechanism by CRHR2 modulates anxiety and its correlation with neuroinflammation remain unclear. Here, we first constructed a crhr2 zebrafish mutant line, and evaluated anxiety-like behaviors, gene expression associated with the HPA axis, neuroinflammatory response, neurotransmitters, and PUFAs profile in crhr2+/+ and crhr2-/- zebrafish. The crhr2 deficiency decreased cortisol levels and up-regulated crhr1 and down-regulated crhb, crhbp, ucn3l and proopiomelanocortin a (pomc a) in zebrafish. Interestingly, a significant increase in the neuroinflammatory markers, translocator protein (TSPO) and the activation of microglia M1 phenotype (CD11b) were found in crhr2-/- zebrafish. As a consequence, the expression of granulocyte-macrophage colony-stimulating factor, pro-inflammatory cytokines vascular endothelial growth factor, and astrocyte A1 phenotype c3 were up-regulated. While microglia anti-inflammatory phenotype (CD206), central anti-inflammatory cytokine interleukin-4, arginase-1, and transforming growth factor-β were downregulated. In parallel, crhr2-deficient zebrafish showed an upregulation of vdac1 protein, a TSPO ligand, and its downstream caspase-3. Furthermore, 5-HT/5-HIAA ratio was decreased and n-3 PUFAs deficiency was identified in crhr2-/- zebrafish. In conclusion, anxiety-like behavior displayed by crhr2-deficient zebrafish may be caused by the HPA axis dysfunction and enhanced neuroinflammation, which resulted in n-3 PUFAs and monoamine neurotransmitter reductions.

Maternal glucocorticoids do not directly mediate the effects of maternal social stress on the fetus

Stress during pregnancy negatively affects the fetus and increases the risk for affective disorders in adulthood. Excess maternal glucocorticoids are thought to mediate fetal programming; however, whether they exert their effects directly or indirectly remains unclear. During pregnancy, protective mechanisms including maternal hypothalamic-pituitary-adrenal (HPA) axis hyporesponsiveness and placental 11β-hydroxysteroid dehydrogenase (11βHSD) type 2, which inactivates glucocorticoids, limit mother-to-fetus glucocorticoid transfer. However, whether repeated stress negatively impacts these mechanisms is not known. Pregnant rats were exposed to repeated social stress on gestational days (GD) 16-20 and several aspects of HPA axis and glucocorticoid regulation, including concentrations of glucocorticoids, gene expression for their receptors (Nr3c1, Nr3c2), receptor chaperones (Fkbp51, Fkbp52) and enzymes that control local glucocorticoid availability (Hsd11b1, Hsd11b2), were investigated in the maternal, placental and fetal compartments on GD20. The maternal HPA axis was activated following stress, though the primary driver was vasopressin, rather than corticotropin-releasing hormone. Despite the stress-induced increase in circulating corticosterone in the dams, only a modest increase was detected in the circulation of female fetuses, with no change in the fetal brain of either sex. Moreover, there was no change in the expression of genes that mediate glucocorticoid actions or modulate local concentrations in the fetal brain. In the placenta labyrinth zone, stress increased Hsd11b2 expression only in males and Fkbp51 expression only in females. Our results indicate that any role glucocorticoids play in fetal programming is likely indirect, perhaps through sex-dependent alterations in placental gene expression, rather than exerting effects via direct crossover into the fetal brain.

Sex-specific plasticity in CRF regulation of inhibitory control in central amygdala CRF1 neurons after chronic voluntary alcohol drinking

Despite strong preclinical evidence for the ability of corticotropin releasing factor 1 (CRF1) antagonists to regulate alcohol consumption, clinical trials have not yet demonstrated therapeutic effects of these compounds in alcohol use disorder (AUD) patients. Several confounding factors may limit the translation of preclinical CRF1 research to patients, including reliance on experimenter-administered alcohol instead of voluntary consumption, a preponderance of evidence collected in male subjects only and an inability to assess the effects of alcohol on specific brain circuits. A population of particular interest is the CRF1-containing neurons of the central amygdala (CeA). CRF1 CeA neurons are sensitive to ethanol, but the effects of alcohol drinking on CRF signalling within this population are unknown. In the present study, we assessed the effects of voluntary alcohol drinking on inhibitory control of CRF1+ CeA neurons from male and female CRF1:GFP mice using ex vivo electrophysiology and determined the contributions of CRF1 signalling to inhibitory control and voluntary alcohol drinking. Chronic alcohol drinking produced neuroadaptations in CRF1+ neurons that increased the sensitivity of GABA_A receptor-mediated sIPSCs to the acute effects of alcohol, CRF and the CRF1 antagonist R121919, but these adaptations were more pronounced in male versus female mice. The CRF1 antagonist CP-154,526 reduced voluntary alcohol drinking in both sexes and abolished sex differences in alcohol drinking. The lack of alcohol-induced adaptation in the female CRF1 system may be related to the elevated alcohol intake exhibited by female mice and could contribute to the ineffectiveness of CRF1 antagonists in female AUD patients.

Long-lasting effects of prenatal stress on HPA axis and inflammation: A systematic review and multilevel meta-analysis in rodent studies

Exposure to prenatal stress (PNS) can lead to long-lasting neurobiological and behavioral consequences for the offspring, which may enhance the susceptibility for mental disorders. The hypothalamus-pituitary-adrenal (HPA) axis and the immune system are two major factors involved in the stress response. Here, we performed a systematic review and meta-analysis of rodent studies that investigated the effects of PNS exposure on the HPA axis and inflammatory cytokines in adult offspring. Our analysis shows that animals exposed to PNS display a consistent increase in peripheral corticosterone (CORT) levels and central corticotrophin-releasing hormone (CRH), while decreased levels of its receptor 2 (CRHR2). Meta-regression revealed that sex and duration of PNS protocol are covariates that moderate these results. There was no significant effect of PNS in glucocorticoid receptor (GR), CRH receptor 1 (CRHR1), pro- and anti-inflammatory cytokines. Our findings suggest that PNS exposure elicits long-lasting effects on the HPA axis function, providing an important tool to investigate in preclinical settings key pathological aspects related to early-life stress exposure. Furthermore, researchers should be aware of the mixed outcomes of PNS on inflammatory markers in the adult brain.

Maternal antioxidant treatment prevents the adverse effects of prenatal stress on the offspring's brain and behavior

Maternal exposure to stress during pregnancy is associated with an increased risk of psychiatric disorders in the offspring in later life. The mechanisms through which the effects of maternal stress are transmitted to the fetus are unclear, however the placenta, as the interface between mother and fetus, is likely to play a key role. Using a rat model, we investigated a role for placental oxidative stress in conveying the effects of maternal social stress to the fetus and the potential for treatment using a nanoparticle-bound antioxidant to prevent adverse outcomes in the offspring.

Maternal psychosocial stress increased circulating corticosterone in the mother, but not in the fetuses. Maternal stress also induced oxidative stress in the placenta, but not in the fetal brain. Blocking oxidative stress using an antioxidant prevented the prenatal stress-induced anxiety phenotype in the male offspring, and prevented sex-specific neurobiological changes, specifically a reduction in dendrite lengths in the hippocampus, as well as reductions in the number of parvalbumin-positive neurons and GABA receptor subunits in the hippocampus and basolateral amygdala of the male offspring. Importantly, many of these effects were mimicked in neuronal cultures by application of placental-conditioned medium or fetal plasma from stressed pregnancies, indicating molecules released from the placenta may mediate the effects of prenatal stress on the fetal brain. Indeed, both placenta-conditioned medium and fetal plasma contained differentially abundant microRNAs following maternal stress, and their predicted targets were enriched for genes relevant to nervous system development and psychiatric disorders.

The results highlight placental oxidative stress as a key mediator in transmitting the maternal social stress effects on the offspring's brain and behavior, and offer a potential intervention to prevent stress-induced fetal programming of affective disorders.

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Social stress in pregnancy induces oxidative stress but is prevented by antioxidant.

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Prenatal stress induces behavioural, neuroanatomical and neurochemical changes.

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Maternal antioxidant treatment prevents stress-induced effects in the offspring.

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Maternal stress alters the balance of microRNAs secreted from the placenta.

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Placental oxidative stress mediates maternal social stress effects on the offspring.

The effect of early and late pharmacological correction with GABA derivatives of psychoemotional state of offspring of rats with experimental preeclampsia

Introduction: Preeclampsia is a serious complication of pregnancy, which increases the risk of anxiety disorders and depression in children at different stages of ontogenesis.

Materials and methods: The psychoemotional state of 70-day-old offspring of rats with experimental preeclampsia (EP) was studied after pharmacological correction from the 40th to 70th day of offspring life with GABA derivatives – succicard (22 mg/kg), salifen (7.5 mg/kg), phenibut (25 mg/kg) and comparison drug pantogam (50 mg) – in the Open field test, the Elevated plus maze test, and the Marble burying test. The above mentioned tests, together with the Porsolt test, were performed at the age of 18 months.

At the second step, the offspring received succicard (44 mg/kg), salifen (15 mg/kg), phenibut (50 mg/kg) and pantogam (100 mg) from the 24th to 25th month of life. After that, the animals were tested.

Results and discussion: The EP progeny had an increased level of anxiety and depression, as well as obsessive-compulsive disorder.

Early GABA derivatives exposure limited anxiety and depression in the animals aged 70 days and 18 months, with salifen limiting compulsive behavior. Late GABA derivatives “treatment” exerted anti-compulsive and antidepressant effects, with phenibut having a greater degree of anxiolytic activity. Succicard, salifen and phenibut were comparable or superior to pantogam in terms of effectiveness.

Conclusion: EP has a negative effect on the psychoemotional state of offspring. Early and late pharmacological correction with derivatives of GABA, such as succicard, salifen and phenibut, reduced anxiety, manifestations of obsessive-compulsive disorder, and depression in offspring of the rats with EP pregnancy.

Biological intersection of sex, age, and environment in the corticotropin releasing factor (CRF) system and alcohol

The neuropeptide corticotropin-releasing factor (CRF) is critical in neural circuit function and behavior, particularly in the context of stress, anxiety, and addiction. Despite a wealth of preclinical evidence for the efficacy of CRF receptor 1 antagonists in reducing behavioral pathology associated with alcohol exposure, several clinical trials have had disappointing outcomes, possibly due to an underappreciation of the role of biological variables. Although he National Institutes of Health (NIH) now mandate the inclusion of sex as a biological variable in all clinical and preclinical research, the current state of knowledge in this area is based almost entirely on evidence from male subjects. Additionally, the influence of biological variables other than sex has received even less attention in the context of neuropeptide signaling. Age (particularly adolescent development) and housing conditions have been shown to affect CRF signaling and voluntary alcohol intake, and the interaction between these biological variables is particularly relevant to the role of the CRF system in the vulnerability or resilience to the development of alcohol use disorder (AUD). Going forward, it will be important to include careful consideration of biological variables in experimental design, reporting, and interpretation. As new research uncovers conditions in which sex, age, and environment play major roles in physiological and/or pathological processes, our understanding of the complex interaction between relevant biological variables and critical signaling pathways like the CRF system in the cellular and behavioral consequences of alcohol exposure will continue to expand ultimately improving the ability of preclinical research to translate to the clinic. This article is part of the special issue on Neuropeptides.

Mechanisms of Shared Vulnerability to Post-traumatic Stress Disorder and Substance Use Disorders

Psychoactive substance use is a nearly universal human behavior, but a significant minority of people who use addictive substances will go on to develop an addictive disorder. Similarly, though ~90% of people experience traumatic events in their lifetime, only ~10% ever develop post-traumatic stress disorder (PTSD). Substance use disorders (SUD) and PTSD are highly comorbid, occurring in the same individual far more often than would be predicted by chance given the respective prevalence of each disorder. Some possible reasons that have been proposed for the relationship between PTSD and SUD are self-medication of anxiety with drugs or alcohol, increased exposure to traumatic events due to activities involved in acquiring illegal substances, or addictive substances altering the brain's stress response systems to make users more vulnerable to PTSD. Yet another possibility is that some people have an intrinsic vulnerability that predisposes them to both PTSD and SUD. In this review, we integrate clinical and animal data to explore these possible etiological links between SUD and PTSD, with an emphasis on interactions between dopaminergic, adrenocorticotropic, GABAergic, and glutamatergic neurobehavioral mechanisms that underlie different emotional learning styles.

G Protein-Coupled Estrogen Receptor in Immune Cells and Its Role in Immune-Related Diseases

G protein-coupled estrogen receptor 1 (GPER1), is a functional estrogen receptor involved in estrogen related actions on several systems including processes of the nervous, reproductive, metabolic, cardiovascular, and immune system. Regarding the latter, GPER is expressed in peripheral B and T lymphocytes as well as in monocytes, eosinophils, and neutrophils. Several studies have implicated GPER in immune-mediated diseases like multiple sclerosis, Parkinson's disease, and atherosclerosis-related inflammation, while a recent report suggests that its deletion could be responsible for a form of familial immunodeficiency. It has also been suggested that it is a key regulator of immune-mediated events in breast, pancreatic, prostate, and hepatocellular cancer as well as in melanoma. GPER has been also reported to interact with classic ER-alpha or its splice variants in order to modify immune functions. This review aims to present current knowledge relating GPER to immune functions, the cellular and signaling pathways involved, as well as the potential clinical implications of GPER modulation in immune-related diseases.

The Effects of Acute Neonatal Pain on Expression of Corticotropin-Releasing Hormone and Juvenile Anxiety in a Rodent Model

Premature infants in the neonatal intensive care unit (NICU) may be subjected to numerous painful procedures without analgesics. One necessary, though acutely painful, procedure is the use of heel lances to monitor blood composition. The current study examined the acute effects of neonatal pain on maternal behavior as well as amygdalar and hypothalamic activation, and the long-term effects of neonatal pain on later-life anxiety-like behavior, using a rodent model. Neonatal manipulations consisted of either painful needle pricks or non-painful tactile stimulation in subjects’ left plantar paw surface which occurred four times daily during the first week of life [postnatal day (PND)1–PND7]. Additionally, maternal behaviors in manipulated litters were compared against undisturbed litters via scoring of videotaped interactions to examine the long-term effects of pain on dam-pup interactions. Select subjects underwent neonatal brain collection (PND6) and fluorescent in situ hybridization (FISH) for corticotropin-releasing hormone (CRH) and the immediate early gene c-fos. Other subjects were raised to juvenile age (PND24 and PND25) and underwent innate anxiety testing utilizing an elevated plus maze (EPM) protocol. FISH indicated that neonatal pain influenced amygdalar CRH and c-fos expression, predominately in males. No significant increase in c-fos or CRH expression was observed in the hypothalamus. Additionally, neonatal pain altered anxiety behaviors independent of sex, with neonatal pain subjects showing the highest frequency of exploratory behavior. Neonatal manipulations did not alter maternal behaviors. Overall, neonatal pain drives CRH expression and produces behavioral changes in anxiety that persist until the juvenile stage.

Perinatal Stress Programs Sex Differences in the Behavioral and Molecular Chronobiological Profile of Rats Maintained Under a 12-h Light-Dark Cycle

Stress and the circadian systems play a major role in an organism's adaptation to environmental changes. The adaptive value of the stress system is reactive while that of the circadian system is predictive. Dysfunctions in these two systems may account for many clinically relevant disorders. Despite the evidence that interindividual differences in stress sensitivity and in the functioning of the circadian system are related, there is limited integrated research on these topics. Moreover, sex differences in these systems are poorly investigated. We used the perinatal stress (PRS) rat model, a well-characterized model of maladaptive programming of reactive and predictive adaptation, to monitor the running wheel behavior in male and female adult PRS rats, under a normal light/dark cycle as well as in response to a chronobiological stressor (6-h phase advance/shift). We then analyzed across different time points the expression of genes involved in circadian clocks, stress response, signaling, and glucose metabolism regulation in the suprachiasmatic nucleus (SCN). In the unstressed control group, we found a sex-specific profile that was either enhanced or inverted by PRS. Also, PRS disrupted circadian wheel-running behavior by inducing a phase advance in the activity of males and hypoactivity in females and increased vulnerability to chronobiological stress in both sexes. We also observed oscillations of several genes in the SCN of the unstressed group in both sexes. PRS affected males to greater extent than females, with PRS males displaying a pattern similar to unstressed females. Altogether, our findings provide evidence for a specific profile of dysmasculinization induced by PRS at the behavioral and molecular level, thus advocating the necessity to include sex as a biological variable to study the set-up of circadian system in animal models.

Exposure to di-(2-ethylhexyl) phthalate transgenerationally alters anxiety-like behavior and amygdala gene expression in adult male and female mice

Phthalates are industrial plasticizers and stabilizers commonly found in polyvinyl chloride plastic and consumer products, including food packaging, cosmetics, medical devices, and children's toys. Di-(2-ethylhexyl) phthalate (DEHP), one of the most commonly used phthalates, exhibits endocrine-disrupting characteristics and direct exposure leads to reproductive deficits and abnormalities in anxiety-related behaviors. Importantly, increasing evidence indicates that the impacts of DEHP exposure on reproduction and social behavior persist across multiple generations. In this study, we tested the hypothesis that transgenerational DEHP exposure alters anxiety-like behavior and neural gene expression in both male and female mice. Pregnant CD-1 mice were orally dosed daily with either tocopherol-stripped corn oil or DEHP (20 or 200 μg/kg/day; 500 or 750 mg/kg/day) from gestational day 10.5 until birth to produce the F1 generation. Females from each generation were bred with untreated, unrelated CD-1 males to produce subsequent generations. Behavior and gene expression assays were performed with adult, intact F3 males and females. Transgenerational DEHP exposure increased time spent in the open arm in the elevated plus maze for adult females (750 mg/kg/day lineage), but not males. In adult females, we observed a down-regulation of mRNA expression of estrogen receptor 1 in the 200 μg/kg/day and 500 mg/kg/day treatment lineages, mineralocorticoid receptor in the 200 μg/kg/day lineage, and dopamine receptor 2 in the 20 μg/kg/day and 750 mg/kg/day lineages. In adult males, we found an up-regulation of estrogen receptor 2 in the 20 and 200 μg/kg/day lineages, and dopamine receptor 1 in the 20 μg/kg/day and 750 mg/kg/day lineages. No hippocampal gene expression modifications were observed in response to treatment. These results implicate dose-specific transgenerational effects on behavior and neural gene expression in adult male and female mice.

Giving a good start to a new life via maternal brain allostatic adaptations in pregnancy

Successful pregnancy requires adjustments to multiple maternal homeostatic mechanisms, governed by the maternal brain to support and enable survival of the growing fetus and placenta. Such adjustments fit the concept of allostasis (stability through change) and have a cost: allostatic load. Allostasis is driven by ovarian, anterior pituitary, placental and feto-placental hormones acting on the maternal brain to promote adaptations that support the pregnancy and protect the fetus. Many women carry an existing allostatic load into pregnancy, from socio-economic circumstances, poor mental health and in 'developed' countries, also from obesity. These pregnancies have poorer outcomes indicating negative interactions (failing allostasis) between pre-pregnancy and pregnancy allostatic loads. Use of animal models, such as adult prenatally stressed female offspring with abnormal neuroendocrine, metabolic and behavioural phenotypes, to probe gene expression changes, and epigenetic mechanisms in the maternal brain in adverse pregnancies are discussed, with the prospect of ameliorating poor pregnancy outcomes.

Sex differences in the hypothalamic-pituitary-adrenal axis' response to stress: an important role for gonadal hormones

The hypothalamic-pituitary-adrenal (HPA) axis, a neuroendocrine network that controls hormonal responses to internal and external challenges in an organism's environment, exhibits strikingly sex-biased activity. In adult female rodents, acute HPA function following a stressor is markedly greater than it is in males, and this difference has largely been attributed to modulation by the gonadal hormones testosterone and estradiol. These gonadal hormones are produced by the hypothalamic-pituitary-gonadal (HPG) axis and have been shown to determine sex differences in adult HPA function after acute stress via their activational and organizational effects. Although these actions of gonadal hormones are well supported, the possibility that sex chromosomes similarly influence HPA activity is unexplored. Moreover, questions remain regarding sex differences in the activity of the HPA axis following chronic stress and the underlying contributions of gonadal hormones and sex chromosomes. The present review examines what is currently known about sex differences in the neuroendocrine response to stress, as well as outstanding questions regarding this sex bias. Although it primarily focuses on the rodent literature, a brief discussion of sex differences in the human HPA axis is also included.

Maternal stress and the MPOA: Activation of CRF receptor 1 impairs maternal behavior and triggers local oxytocin release in lactating rats

Maternal behavior and anxiety are potently modulated by the brain corticotropin-releasing factor (CRF) system postpartum. Downregulation of CRF in limbic brain regions is essential for appropriate maternal behavior and an adaptive anxiety response. Here, we focus our attention on arguably the most important brain region for maternal behavior, the hypothalamic medial preoptic area (MPOA). Within the MPOA, mRNA for CRF receptor subtype 1 (protein: CRFR1, gene: Crhr1) was more abundantly expressed than for subtype 2 (protein: CRFR2, gene: Crhr2), however expression of Crhr1, Crhr2 and CRF-binding protein (protein: CRFBP, gene: Crhbp) mRNA was similar between virgin and lactating rats. Subtype-specific activation of CRFR, predominantly CRFR1, in the MPOA decreased arched back nursing and total nursing under non-stress conditions. Following acute stressor exposure, only CRFR1 inhibition rescued the stress-induced reduction in arched back nursing while CRFR1 activation prolonged the decline in nursing. Furthermore, inhibition of CRFR1 strongly increased maternal aggression in the maternal defense test. CRFR1 activation had anxiogenic actions and reduced locomotion on the elevated plus-maze, however neither CRFR1 nor R2 manipulation affected maternal motivation. In addition, activation of CRFR1, either centrally or locally in the MPOA, increased local oxytocin release. Finally, inhibition of CRFBP (a potent regulator of CRFR activity) in the MPOA did not affect any of the maternal parameters investigated. In conclusion, activity of CRFR in the MPOA, particularly of subtype 1, needs to be dampened during lactation to ensure appropriate maternal behavior. Furthermore, oxytocin release in the MPOA may provide a regulatory mechanism to counteract the negative impact of CRFR activation on maternal behavior.

Modulation of the Hypothalamic-Pituitary-Adrenal Axis by Early Life Stress Exposure

Exposure to stress during critical periods in development can have severe long-term consequences, increasing overall risk on psychopathology. One of the key stress response systems mediating these long-term effects of stress is the hypothalamic-pituitary-adrenal (HPA) axis; a cascade of central and peripheral events resulting in the release of corticosteroids from the adrenal glands. Activation of the HPA-axis affects brain functioning to ensure a proper behavioral response to the stressor, but stress-induced (mal)adaptation of the HPA-axis' functional maturation may provide a mechanistic basis for the altered stress susceptibility later in life. Development of the HPA-axis and the brain regions involved in its regulation starts prenatally and continues after birth, and is protected by several mechanisms preventing corticosteroid over-exposure to the maturing brain. Nevertheless, early life stress (ELS) exposure has been reported to have numerous consequences on HPA-axis function in adulthood, affecting both its basal and stress-induced activity. According to the match/mismatch theory, encountering ELS prepares an organism for similar ("matching") adversities during adulthood, while a mismatching environment results in an increased susceptibility to psychopathology, indicating that ELS can exert either beneficial or disadvantageous effects depending on the environmental context. Here, we review studies investigating the mechanistic underpinnings of the ELS-induced alterations in the structural and functional development of the HPA-axis and its key external regulators (amygdala, hippocampus, and prefrontal cortex). The effects of ELS appear highly dependent on the developmental time window affected, the sex of the offspring, and the developmental stage at which effects are assessed. Albeit by distinct mechanisms, ELS induced by prenatal stressors, maternal separation, or the limited nesting model inducing fragmented maternal care, typically results in HPA-axis hyper-reactivity in adulthood, as also found in major depression. This hyper-activity is related to increased corticotrophin-releasing hormone signaling and impaired glucocorticoid receptor-mediated negative feedback. In contrast, initial evidence for HPA-axis hypo-reactivity is observed for early social deprivation, potentially reflecting the abnormal HPA-axis function as observed in post-traumatic stress disorder, and future studies should investigate its neural/neuroendocrine foundation in further detail. Interestingly, experiencing additional (chronic) stress in adulthood seems to normalize these alterations in HPA-axis function, supporting the match/mismatch theory.

CYP2D6 polymorphisms and their influence on risperidone treatment

Cytochrome P450 enzyme especially CYP2D6 plays a major role in biotransformation. The interindividual variations of treatment response and toxicity are influenced by the polymorphisms of this enzyme. This review emphasizes the effect of CYP2D6 polymorphisms in risperidone treatment in terms of basic knowledge, pharmacogenetics, effectiveness, adverse events, and clinical practice. Although the previous studies showed different results, the effective responses in risperidone treatment depend on the CYP2D6 polymorphisms. Several studies suggested that CYP2D6 polymorphisms were associated with plasma concentration of risperidone, 9-hydroxyrisperidone, and active moiety but did not impact on clinical outcomes. In addition, CYP2D6 poor metabolizer showed more serious adverse events such as weight gain and prolactin than other predicted phenotype groups. The knowledge of pharmacogenomics of CYP2D6 in risperidone treatment is increasing, and it can be used for the development of personalized medication in term of genetic-based dose recommendation. Moreover, the effects of many factors in risperidone treatment are still being investigated. Both the CYP2D6 genotyping and therapeutic drug monitoring are the important steps to complement the genetic-based risperidone treatment.

Protective effect of early prenatal stress on the induction of asthma in adult mice: Sex-specific differences

Adversities faced during the prenatal period can be related to the onset of diseases in adulthood. However, little is known about the effects on the respiratory system. This study aimed to evaluate the effects of prenatal stress in two different time-points during pregnancy on pulmonary function and on the inflammatory profile of mice exposed to an asthma model. Male and female BALB/c mice were divided into 3 groups: control (CON), prenatal stress from the second week of pregnancy (PNS1) and prenatal stress on the last week of pregnancy (PNS2). Both PNS1 and PNS2 pregnant females were submitted to restraint stress. As adults, fear/anxiety behaviors were assessed, and animals were subjected to an asthma model induced by ovalbumin. Pulmonary function, inflammatory parameters in bronchoalveolar lavage (BAL) and histology were evaluated. There was a significant decrease in the number of entries and time spent in the central quadrant on the open field test for the PNS1 animals. Females (PNS1) showed improved pulmonary function (airway resistance, tissue damping and pulmonary elastance), significant increase in the percentage of neutrophils and lymphocytes and a decrease in eosinophils when compared to controls. There was a significant decrease in inflammatory cytokines in BAL of both males (IL-5 and IL-13) and females (IL-4, IL-5 and IL-13) from PNS1 and PNS2 when compared to the CON group. Prenatal stress starting from the beginning of pregnancy reduces the impact of asthma development in adult female mice, showing an improved pulmonary function and a lower inflammatory response in the lungs.

Sex- and corticotropin-releasing factor receptor 2- dependent actions of urocortin 1 during inflammation

We investigated whether corticotropin-releasing factor receptor 2 (CRF2) and its high-affinity agonist urocortin 1 (Ucn1) mediate sex-specific signaling and immune responses. Intrarectal trinitrobenzene sulfonic acid was used to induce experimental colitis in wild-type, CRF2 knockout (CRF2KO), and heterozygous (CRF2Ht) mice of both sexes. Changes in plasma extravasation, organ weight, survival, immune cell numbers, inflammatory cytokines, and the MAPK signaling pathway were assessed. Stored intestinal biopsies from patients with Crohn's disease (CD) and age- and sex-matched individuals without inflammatory bowel disease (IBD) were examined by immunofluorescence and confocal microscopy to characterize Ucn1 and CRF receptor expression. CRF2Ht mice of both sexes showed decreased survival during colitis compared with other genotypes. Ucn1 improved survival in male mice alone. Ucn1 restored colon length and spleen and adrenal weight and decreased colonic TNF-α, IL-6, and IL-1β levels in male CRF2Ht mice alone. CRF2Ht mice of both sexes showed decreased phosphorylation of MAPK p38 and heat shock protein 27 (Hsp27) levels. Ucn1 restored p-Hsp27 levels in male CRF2Ht mice alone. Expression of the chaperone protein Hsp90 decreased during colitis, except in male CRF2Ht mice. Taken together, our data indicate that sex shows significant interaction with genotype and Ucn1 during colitis. Human duodenal and colonic biopsies revealed that sex-specific differences exist in levels of CRF receptors and Ucn1 expression in patients with CD compared with the matched non-IBD subjects. To conclude, Ucn1 mediates sex-specific immune and cellular signaling responses via CRF2, emphasizing the need for inclusion of females in preclinical studies.

CRF-R1 activation in the anterior-dorsal BNST induces maternal neglect in lactating rats via an HPA axis-independent central mechanism

Adequate maternal behavior in rats requires minimal corticotropin-releasing factor receptor (CRF-R) activation in the medial-posterior bed nucleus of the stria terminalis (mpBNST). Based on the architectural heterogeneity of the BNST and its distinct inter-neural connectivity, we tested whether CRF-R manipulation in another functional part, the anterior-dorsal BNST (adBNST), differentially modulates maternal behavior. We demonstrate that in the adBNST, activation of CRF-R1 reduced arched back nursing (ABN) and nursing, whereas activation of CRF-R2 resulted in an initial reduction in nursing but significantly increased the incidence of ABN 5h after the treatment. Following stressor exposure, which is detrimental to maternal care, ABN tended to be protected by CRF-R1 blockade. Maternal motivation, maternal aggression, and anxiety were unaffected by any manipulation. Furthermore, under basal and stress conditions, activation of adBNST CRF-R1 increased plasma ACTH and corticosterone concentrations, whereas stimulation of adBNST CRF-R2 increased basal plasma ACTH and corticosterone concentrations, but blocked the stress-induced increase in plasma corticosterone secretion. Moreover, both the CRF-R1 and -R2 antagonists prevented the stress-induced increase in plasma corticosterone secretion. Importantly, elevated levels of circulating corticosterone induced by intra-adBNST administration of CRF-R1 or -R2 agonist did not impact maternal care. Finally, Crf mRNA expression in the adBNST was increased during lactation; however, Crfr1 mRNA expression was similar between lactating and virgin rats. In conclusion, maternal care is impaired by adBNST CRF-R1 activation, and this appears to be the result of a central action, rather than an effect of elevated circulating levels of CORT. These data provide new insights into potential causes of disturbed maternal behavior postpartum.

Prenatal stress programs neuroendocrine stress responses and affective behaviors in second generation rats in a sex-dependent manner

An adverse environment in early life is often associated with dysregulation of the hypothalamo-pituitary-adrenal (HPA) axis and higher rates of mood disorders in adulthood. In rats, exposure to social stress during pregnancy results in hyperactive HPA axis responses to stress in the adult offspring and heightened anxiety behavior in the males, but not the females. Here we tested whether, without further intervention, the effects of prenatal stress (PNS) in the first filial generation (F1) are transmitted to the F2 generation via the maternal line. F1 control and PNS female rats were mated with control males and housed under non-stress conditions throughout pregnancy. HPA axis responses to acute stress, anxiety- and depressive-like behavior were assessed in the adult F2 offspring. ACTH and corticosterone responses to an acute stressor were markedly enhanced in F2 PNS females compared with controls. This was associated with greater corticotropin releasing hormone (Crh) mRNA expression in the paraventricular nucleus and reduced hippocampal glucocorticoid (Gr) and mineralocorticoid receptor (Mr) mRNA expression. Conversely, in the F2 PNS males, HPA axis responses to acute stress were attenuated and hippocampal Gr mRNA expression was greater compared with controls. F2 PNS males exhibited heightened anxiety-like behavior (light-dark box and elevated plus maze) compared with F2 control males. Anxiety-like behavior did not differ between F2 control and PNS females during metestrus/diestrus, however at proestrus/estrus, F2 control females displayed a reduction in anxiety-like behavior, but this effect was not observed in the F2 PNS females. Heightened anxiety in the F2 PNS males was associated with greater Crh mRNA expression in the central nucleus of the amygdala compared with controls. Moreover, Crh receptor-1 (Crhr1) mRNA expression was significantly increased, whereas Crhr2 mRNA was significantly decreased in discrete regions of the amygdala in F2 PNS males compared with controls, with no differences in the F2 females. No differences in depressive-like behavior (sucrose preference or forced swim test) were observed in either sex. In conclusion, the effects of maternal stress during pregnancy on HPA axis regulation and anxiety-like behavior can be transmitted to future generations in a sex-dependent manner. These data have implications for human neuropsychiatric disorders with developmental origins.

Programming the brain and behaviour by early-life stress: a focus on neuroactive steroids

Animal studies have amply demonstrated that stress exposure during pregnancy or in early postnatal life can adversely influence brain development and have long-term 'programming' effects on future brain function and behaviour. Furthermore, a growing body of evidence from human studies supports the hypothesis that some psychiatric disorders may have developmental origins. Here, the focus is on three adverse consequences of early-life stress: dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, heightened anxiety behaviour and cognitive impairments, with review of what is known about the underlying central mechanisms. Neuroactive steroids modulate neuronal activity and play a key role in neurodevelopment. Moreover they can negatively modulate activity of the HPA axis, exert anxiolytic actions and influence cognitive performance. Thus, neuroactive steroids may provide a link between early-life stress and the resultant adverse effects on the brain and behaviour. Here, a role for neuroactive steroids, in particular the 5α-reduced/3α-hydroxylated metabolites of progesterone, testosterone and deoxycorticosterone, is discussed in the context of early-life stress. Furthermore, the impact of early-life stress on the brain's capacity to generate neurosteroids is considered and the evidence for an ability of neuroactive steroids to over-write the negative effects of early-life stress on the brain and behaviour is examined. An enhanced understanding of the influence of early-life stress on brain neurosteroid systems could aid the identification of new targets for developing treatments for stress-related conditions in humans.

Changes induced by prenatal stress in behavior and brain morphology: can they be prevented or reversed?

This chapter presents a critical analysis of the behavioral alterations reported in the offspring of women exposed to stress and/or depression during pregnancy and the neurochemical and structural changes underlying them. Among the alterations attributed to prenatal stress in humans and experimental rats of both sexes is impaired regulation of the hypothalamic-pituitary-adrenal (HPA) axis, anxiety and exaggerated fear of novelty, and decreased social interaction. Learning and attention deficits are more prevalent in boys and male rats. Fear of novelty and anxiety are associated with enlargement of the amygdala and its corticotropin-releasing factor content, and decreased socialization, with lower oxytocin activity in the amygdala. Learning deficits are associated with a decrease in neurogenesis, dendritic complexity, and spine number in the dorsal hippocampus. Fostering prenatally stressed (PS) pups onto control mothers prevents the dysregulation of the HPA axis and heightened anxiety, indicating a role for postnatal factors in their etiology. By contrast, learning impairment and decreased socialization are not affected by this fostering procedure and are therefore prenatally mediated.In spite of their widespread use in depressed pregnant women, selective serotonin reuptake inhibitor (SSRI) antidepressants do not normalize the behavior of their children. When administered during gestation to stressed rats, SSRIs do not reduce anxiety or learning deficits in their offspring. Moreover, when given to unstressed mothers, SSRIs induce anxiety in the offspring. The detrimental effect of SSRIs may result from inhibition of the serotonin transporter exposing the brain to excess amounts of 5-hydroxytryptamine (5-HT) at a critical time during fetal development.

The consequences of early-life adversity: neurobiological, behavioural and epigenetic adaptations

During the perinatal period, the brain is particularly sensitive to remodelling by environmental factors. Adverse early-life experiences, such as stress exposure or suboptimal maternal care, can have long-lasting detrimental consequences for an individual. This phenomenon is often referred to as 'early-life programming' and is associated with an increased risk of disease. Typically, rodents exposed to prenatal stress or postnatal maternal deprivation display enhanced neuroendocrine responses to stress, increased levels of anxiety and depressive-like behaviours, and cognitive impairments. Some of the phenotypes observed in these models of early-life adversity are likely to share common neurobiological mechanisms. For example, there is evidence for impaired glucocorticoid negative-feedback control of the hypothalamic-pituitary-adrenal axis, altered glutamate neurotransmission and reduced hippocampal neurogenesis in both prenatally stressed rats and rats that experienced deficient maternal care. The possible mechanisms through which maternal stress during pregnancy may be transmitted to the offspring are reviewed, with special consideration given to altered maternal behaviour postpartum. We also discuss what is known about the neurobiological and epigenetic mechanisms that underpin early-life programming of the neonatal brain in the first generation and subsequent generations, with a view to abrogating programming effects and potentially identifying new therapeutic targets for the treatment of stress-related disorders and cognitive impairment.

Hypoactivation of CRF receptors, predominantly type 2, in the medial-posterior BNST is vital for adequate maternal behavior in lactating rats

Maternal behavior ensures the proper development of the offspring. In lactating mammals, maternal behavior is impaired by stress, the physiological consequence of central corticotropin-releasing factor receptor (CRF-R) activation. However, which CRF-R subtype in which specific brain area(s) mediates this effect is unknown. Here we confirmed that an intracerebroventricularly injected nonselective CRF-R antagonist enhances, whereas an agonist impairs, maternal care. The agonist also prolonged the stress-induced decrease in nursing, reduced maternal aggression and increased anxiety-related behavior. Focusing on the bed nucleus of the stria terminalis (BNST), CRF-R1 and CRF-R2 mRNA expression did not differ in virgin versus lactating rats. However, CRF-R2 mRNA was more abundant in the posterior than in the medial BNST. Pharmacological manipulations within the medial-posterior BNST showed that both CRF-R1 and CRF-R2 agonists reduced arched back nursing (ABN) rapidly and after a delay, respectively. After stress, both antagonists prevented the stress-induced decrease in nursing, with the CRF-R2 antagonist actually increasing ABN. During the maternal defense test, maternal aggression was abolished by the CRF-R2, but not the CRF-R1, agonist. Anxiety-related behavior was increased by the CRF-R1 agonist and reduced by both antagonists. Both antagonists were also effective in virgin females but not in males, revealing a sexual dimorphism in the regulation of anxiety within the medial-posterior BNST. In conclusion, the detrimental effects of increased CRF-R activation on maternal behavior are mediated via CRF-R2 and, to a lesser extent, via CRF-R1 in the medial-posterior BNST in lactating rats. Moreover, both CRF-R1 and CRF-R2 regulate anxiety in females independently of their reproductive status.

CRF type 1 receptors of the medial amygdala modulate inhibitory avoidance responses in the elevated T-maze

Corticotropin-releasing factor (CRF) plays a critical role in the mediation of physiological and behavioral responses to stressors. In the present study, we investigated the role played by the CRF system within the medial amygdala (MeA) in the modulation of anxiety and fear-related responses. Male Wistar rats were bilaterally administered into the MeA with CRF (125 and 250 ng/0.2μl, experiment 1) or with the CRFR1 antagonist antalarmin (25 ng/0.2 μl, experiment 2) and 10 min later tested in the elevated T-maze (ETM) for inhibitory avoidance and escape measurements. In clinical terms, these responses have been respectively related to generalized anxiety and panic disorder. To further verify if the anxiogenic effects of CRF were mediated by CRFR1 activation, we also investigated the effects of the combined treatment with CRF (250 ng/0.2 μl) and antalarmin (25 ng/0.2 μl) (experiment 3). All animals were tested in an open field, immediately after the ETM, for locomotor activity assessment. Results showed that CRF, in the two doses administered, facilitated ETM avoidance, an anxiogenic response. Antalarmin significantly decreased avoidance latencies, an anxiolytic effect, and was able to counteract the anxiogenic effects of CRF. None of the compounds administered altered escape responses or locomotor activity measurements. These results suggest that CRF in the MeA exerts anxiogenic effects by activating type 1 receptors, which might be of relevance to the physiopathology of generalized anxiety disorder.

Allopregnanolone in the brain: protecting pregnancy and birth outcomes

A successful pregnancy requires multiple adaptations in the mother's brain that serve to optimise foetal growth and development, protect the foetus from adverse prenatal programming and prevent premature delivery of the young. Pregnancy hormones induce, organise and maintain many of these adaptations. Steroid hormones play a critical role and of particular importance is the progesterone metabolite and neurosteroid, allopregnanolone. Allopregnanolone is produced in increasing amounts during pregnancy both in the periphery and in the maternal and foetal brain. This review critically examines a role for allopregnanolone in both the maternal and foetal brain during pregnancy and development in protecting pregnancy and birth outcomes, with particular emphasis on its role in relation to stress exposure at this time. Late pregnancy is associated with suppressed stress responses. Thus, we begin by considering what is known about the central mechanisms in the maternal brain, induced by allopregnanolone, that protect the foetus(es) from exposure to harmful levels of maternal glucocorticoids as a result of stress during pregnancy. Next we discuss the central mechanisms that prevent premature secretion of oxytocin and consider a role for allopregnanolone in minimising the risk of preterm birth. Allopregnanolone also plays a key role in the foetal brain, where it promotes development and is neuroprotective. Hence we review the evidence about disruption to neurosteroid production in pregnancy, through prenatal stress or other insults, and the immediate and long-term adverse consequences for the offspring. Finally we address whether progesterone or allopregnanolone treatment can rescue some of these deficits in the offspring.

Sex difference in urocortin production is contributory to the gender disparity in a rat model of vasculitis induced by sodium laurate

Cardiovascular diseases, the most common leading death diseases, occur more in men than women of the same ages. Increasing evidence shows that urocortin (Ucn1), an autocrine or paracrine pro-inflammatory factor, can be regulated by sex hormones. The purpose of the study is to investigate the role of Ucn1 in gender disparity in a sodium laurate-induced vasculitis model. Rats exhibited visible signs of vasculitis on the 14th day after sodium laurate injection. Inflammatory states of the rat femoral artery were observed by histological examination. Significant gender disparity, with the symptoms much grosser in males than females, was seen. In males, the serum levels of Ucn1, prostaglandin estradiol, and soluble intercellular adhesion molecule-1 and the expressions of Ucn1, cyclooxygenase-2, and intercellular adhesion molecule-1 in femoral artery were higher than those in females. Orchidectomy significantly ameliorated the symptoms of vasculitis accompanied with a decrease in the plasma Ucn1 level. However, estradiol supplement after orchidectomy failed to improve the inflammatory states further. In females, ovariectomy and/or dihydrotestosterone supplement significantly increased Ucn1 level and exacerbated symptoms of vasculitis. Furthermore, ip administration of rabbit antiserum to Ucn1 almost abolished the gender differences in vasculitis. These results demonstrated that vasculitis of this model is androgen-responsive and hormonal manipulation by surgical orchidectomy could substantially attenuate the symptoms of vasculitis. Moreover, Ucn1 is a contributory factor to the gender disparity in vasculitis and dihydrotestosterone-promoted Ucn1 secretion exacerbated the development of vasculitis.

Effects of maternal exposure to social stress during pregnancy: consequences for mother and offspring

A suboptimalin uteroenvironment, for example, as a result of maternal stress, can have detrimental effects on the pregnancy and long-term adverse ‘programming’ effects on the offspring. This article focuses on the effects of prenatal social stress on the mother, her pregnancy and the offspring, since these issues have ethological relevance in both animals and humans. The consequences of social stress exposure depend on when during pregnancy the stress occurs, and many of the effects on the offspring are sex specific. Social stress during early pregnancy tends to result in pregnancy loss, whereas stress exposure later in pregnancy, when the mother has already invested considerable resources in the foetuses, results in programmed offspring of low birth weight: a risk factor for various adulthood diseases. Neuroendocrine and behavioural responses to stress in the offspring are particularly sensitive to foetal programming by prenatal stress, indicated by enhanced hypothalamo-pituitary–adrenal (HPA) axis responses and increased anxiety behaviour, which result from permanent changes in the offspring's brain. The dysregulation of HPA axis function may also interfere with other systems, for example, the hypothalamic–pituitary–gonadal axis, as there is evidence for alterations in steroidogenesis, reproductive potential and impaired reproductive/social behaviours in prenatally stressed offspring. Prenatal social stress also programmes future maternal behaviour, highlighting the potential for negative phenotypes to be transmitted to future generations. The possible mechanisms through which maternal stress during pregnancy is transmitted to the foetuses and the foetal brain is programmed by prenatal stress and the potential to overwrite programming of the offspring are discussed.

Sex differences in anxiety and emotional behavior

Research has elucidated causal links between stress exposure and the development of anxiety disorders, but due to the limited use of female or sex-comparative animal models, little is known about the mechanisms underlying sex differences in those disorders. This is despite an overwhelming wealth of evidence from the clinical literature that the prevalence of anxiety disorders is about twice as high in women compared to men, in addition to gender differences in severity and treatment efficacy. We here review human gender differences in generalized anxiety disorder, panic disorder, posttraumatic stress disorder and anxiety-relevant biological functions, discuss the limitations of classic conflict anxiety tests to measure naturally occurring sex differences in anxiety-like behaviors, describe sex-dependent manifestation of anxiety states after gestational, neonatal, or adolescent stressors, and present animal models of chronic anxiety states induced by acute or chronic stressors during adulthood. Potential mechanisms underlying sex differences in stress-related anxiety states include emerging evidence supporting the existence of two anatomically and functionally distinct serotonergic circuits that are related to the modulation of conflict anxiety and panic-like anxiety, respectively. We discuss how these serotonergic circuits may be controlled by reproductive steroid hormone-dependent modulation of crfr1 and crfr2 expression in the midbrain dorsal raphe nucleus and by estrous stage-dependent alterations of γ-aminobutyric acid (GABAergic) neurotransmission in the periaqueductal gray, ultimately leading to sex differences in emotional behavior.

Corticotropin-releasing hormone receptor 1 gene variants in irritable bowel syndrome

BACKGROUND

Corticotropin-releasing hormone (CRH) acts mainly via the CRH receptor 1 (CRH-R1) and plays a crucial role in the stress-induced pathophysiology of irritable bowel syndrome (IBS). Several studies have demonstrated that variants of the CRH-R1 gene carry a potential risk for depression, but evidence for an association between CRH-R1 genotypes and IBS is lacking. We tested the hypothesis that genetic polymorphisms and haplotypes of CRH-R1 moderate the IBS phenotype and negative emotion in IBS patients.

METHODS

A total of 103 patients with IBS and 142 healthy controls participated in the study. Three single-nucleotide polymorphisms of the CRH-R1 gene (rs7209436, rs242924, and rs110402) were genotyped. Subjects' emotional states were evaluated using the Perceived-Stress Scale, the State-Trait Anxiety Inventory, and the Self-rating Depression Scale.

RESULTS

The TT genotype of rs7209436 (P = 0.01) and rs242924 (P = 0.02) was significantly more common in patients with IBS than in controls. Total sample analysis showed significant association between bowel pattern (normal, diarrhea, constipation, or mixed symptoms) and the T allele of rs7209436 (P = 0.008), T allele of rs242924 (P = 0.019), A allele of rs110402 (P = 0.047), and TAT haplocopies (P = 0.048). Negative emotion was not associated with the examined CRH-R1 SNPs.

CONCLUSION

These findings suggest that genetic polymorphisms and the CRH-R1 haplotypes moderate IBS and related bowel patterns. There was no clear association between CRH-R1 genotypes and negative emotion accompanying IBS. Further studies on the CRH system are therefore warranted.