Malfunctioning of the hypothalmaic-pituitary-adrenal (HPA) axis may be related to numerous pathologies, such as depression and post-traumatic stress disorder (PTSD). Pre-clinical studies indicate that early life events during the stress hyporesponsive period (such as 24h maternal deprivation (MD) in rats) produce changes similar to those observed in depression, suggesting that MD may, eventually, be used as an animal model of psychopathology. MD during days 3 and 4 of life (MD3-4) results in higher levels of ACTH, whereas MD11-12 leads to reduction of ACTH secretion. One of the aspects that must be clarified in regard to the consequences of MD3-4 or MD11-12 is related to possible changes in the negative feedback system. The use of a synthetic corticoid, such as Dexamethasone (DEXA) is an useful tool to study this system. Therefore, in the present study, we will investigate the effectiveness of the negative feedback system in MD3-4 and MD11-12 adult rats by injecting DEXA and assssing corticosterone plasma levels in male and female rats.
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