Site at Which α-Ethyltryptamine Acts To Inhibit the Secretion of ACTH

Abstract

α-Ethyltryptamine inhibits ACTH secretion in surgically stressed dogs. It does not appear to act directly on the pituitary because it was without effect on the high level of ACTH secretion in dogs with “hypothalamic islands.” It blocked the increase in ACTH secretion produced by stimulation of the femoral nerve, stimulation of the caudal end of the medulla oblongata, and stimulation of the bundle of Schiitz and the mammillary peduncle in dogs with stereotaxically implanted electrodes. However, stimulation of the ventral hypothalamus, and particularly the median eminence, produced an increase in 17-hydroxycorticoid secretion which was not blocked by α-ethyltryptamine. Therefore, it appears that α-ethyltryptamine produces inhibition of ACTH secretion by an action on the hypothalamus, and it is suggested that it may prevent stimulation of the CRF-secreting neurons by impulses in the incoming afferent fibers. (Endocrinology76: 526,1965)