Feedback effects of dexamethasone on adrenocortical responses in rats with fornix section.

To investigate the sites of the negative feedback of corticoids in the regulation of ACTH secretion, the effect of 10 mug of dexamethasone on adrenocortical responses to ether stress was studied in intact and fornix-sectioned rats. Dexamethasone pretreatment in both groups depressed significantly both the basal and stress plasma corticosterone levels. However, in rats with fornix section the amount of depression of the adrenocortical response was much smaller than in intact animals, when compared to the non-treated group. These data would inicate that extrahypothalamic regions play a role in the action of glucocorticoids in the feedback control of pituitary-adrenal function and that the hippocampus participates in this mechaism.