Adolescent chronic stress causes hypothalamo-pituitary-adrenocortical hypo-responsiveness and depression-like behavior in adult female rats.

Adolescence is a period of substantial neuroplasticity in stress regulatory neurocircuits. Chronic stress exposure during this period leads to long-lasting changes in neuroendocrine function and emotional behaviors, suggesting adolescence may be a critical period for development of stress vulnerability. This study investigated the effects of exposure to 14 days of chronic variable stress (CVS) in late-adolescent (pnd 45-58) female rats on neuroendocrine function, neuropeptide mRNA expression and depressive-like behavior in adolescence (pnd 59) and in adulthood (pnd 101). Adult females exposed to CVS in adolescence have a blunted hypothalamo-pituitary-adrenocortical (HPA) axis in response to a novel stressor and increased immobility in the forced swim test. Blunted HPA axis responses were accompanied by reduced vasopressin mRNA expression in the paraventricular nucleus of the hypothalamus (PVN), suggesting decreased central drive. Adolescent females tested immediately after CVS did not exhibit differences in stress reactivity or immobility in the forced swim test, despite evidence for enhanced central HPA axis drive (increased CRH mRNA expression in PVN). Overall, our study demonstrates that exposure to chronic stress in adolescence is sufficient to induce lasting changes in neuroendocrine drive and behavior, potentially altering the developmental trajectory of stress circuits as female rats age into adulthood.