EFFECT OF DEXAMETHASONE ON ADRENOCORTICAL RESPONSES IN INTACT AND HYPOTHALAMIC DEAFFERENTED RATS

Abstract

The effects of systemically administered dexamethasone on adrenocortical responses to ether stress were studied in intact and in hypothalamic deafferented rats, in which a hypothalamic island was produced. The inhibitory effect of dexamethasone was twice as marked in the intact animals than in the rats with hypothalamic islands. However, direct implantation of dexamethasone into the mediobasal hypothalamus depressed the adrenocortical responses to the same extent in the intact and the deafferented rats. These results would indicate that the negative feedback of dexamethasone in the regulation of ACTH secretion is exerted at hypothalamic levels and that other extra-hypothalamic structures also participate in this mechanism.