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

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

Exercise before pregnancy attenuates the effects of prenatal stress in adult mice in a sex-dependent manner.

The present study aimed to investigate the long-term effects of exercise before pregnancy on changes induced by prenatal stress. Female and male Balb/c mice were divided into three groups: control (CON), prenatal restraint stress (PNS), and exercise before the gestational period plus PNS (EX + PNS). As adult, fear/anxiety behavior, corticosterone secretion, expression of hypothalamic-pituitary-adrenal (HPA)-related genes, as well as epigenetic modifications were evaluated. Exercise before gestation did not prevent the increased fear/anxiety behavior in PNS mice. A nearly significant (p = .06) basal corticosterone increase was observed in PNS males and the exercise before pregnancy reduced the stress-induced corticosterone increase in PNS females. In addition, an increase on prefrontal cortex (PFC) CRHR1 gene expression was observed in PNS females, which was attenuated by the exercise before gestation. We have also found a glucocorticoid receptor (GR) gene expression decrease in the prefrontal cortex in PNS males, as well as a histone H3 acetylation decrease (p = .06) close to the significance level. In conclusion, pregestational exercise may attenuate developmental changes induced by prenatal stress in a sex-dependent manner.

Effects of fluoxetine on CRF and CRF1 expression in rats exposed to the learned helplessness paradigm.

RATIONALE: Stress is a common antecedent reported by people suffering major depression. In these patients, extrahypothalamic brain areas, like the hippocampus and basolateral amygdala (BLA), have been found to be affected. The BLA synthesizes CRF, a mediator of the stress response, and projects to hippocampus. The main hippocampal target for this peptide is the CRF subtype 1 receptor (CRF1). Evidence points to a relationship between dysregulation of CRF/CRF1 extrahypothalamic signaling and depression. OBJECTIVE: Because selective serotonin reuptake inhibitors (SSRIs) are the first-line pharmacological treatment for depression, we investigated the effect of chronic treatment with the SSRI fluoxetine on long-term changes in CRF/CRF1 signaling in animals showing a depressive-like behavior. METHODS: Male Wistar rats were exposed to the learned helplessness paradigm (LH). After evaluation of behavioral impairment, the animals were treated with fluoxetine (10 mg/kg i.p.) or saline for 21 days. We measured BLA CRF expression with RT-PCR and CRF1 expression in CA3 and the dentate gyrus of the hippocampus with in situ hybridization. We also studied the activation of one of CRF1's major intracellular signaling targets, the extracellular signal-related kinases 1 and 2 (ERK1/2) in CA3. RESULTS: In saline-treated LH animals, CRF expression in the BLA increased, while hippocampal CRF1 expression and ERK1/2 activation decreased. Treatment with fluoxetine reversed the changes in CRF and CRF1 expressions, but not in ERK1/2 activation. CONCLUSION: In animals exposed to the learned helplessness paradigm, there are long-term changes in CRF and CRF1 expression that are restored with a behaviorally effective antidepressant treatment.

CRH-stimulation of cyclic adenosine 5'-monophosphate pathway is partially inhibited by the coexpression of CRH-R1 and CRH-R2alpha.

Corticotropin-releasing hormone (CRH) is one of the major proteins responsible for brain stress regulation. Two well-known receptors have been described: type 1 and type 2alpha, both members of the receptor superfamily of G protein-coupled receptors (GPCR). We investigated receptor regulation when both CRH receptor subtypes are coexpressed in the same mammalian cell line. When both types of receptors are coexpressed, cAMP second messenger production is partially inhibited compared to when receptors are expressed separately. However, neither binding kinetics nor internalization rates are modified by coexpression of these receptors. To our knowledge this is the first demonstration of receptor interaction that results in the modification of CRH-mediated signal transduction pathway. Because CRH-R1 and CRH-R2alpha have overlapping mRNA expression patterns in the brain, these receptors may be coexpressed in neurons, suggesting that receptor interaction may play an important role in the effect evoked by CRH, contributing to the complexity of differential coupling of the CRH receptors in different endocrine and stress behavior responses.