Effects of intrahypothalamic crystalline steroids on acute ACTH secretion

Abstract

The respective roles of the hypothalamus and pituitary gland, in the inhibition of adrenocorticotropin secretion by corticoids, were studied by implanting small quantities of crystalline cortisol acetate in the median eminence region and pituitary of male rats. Adrenal weights and adrenal ascorbic acid depletion (AAAD) in response to the acute stress of unilateral adrenalectomy were measured 5, 10, 13, or 21 days postoperatively. Ten days following implantation in the hypothalamus, rats showed adrenal atrophy and inhibition of AAAD. Normal AAAD and slight adrenal hypertrophy were found 10 days after similar implantation of testosterone propionate in the median eminence. Animals with cortisol implants in the pituitary had normal adrenal weights and AAAD responses at this time. In rats with cortisol implants in the hypothalamus, an inhibition of AAAD was present after 5–6 days, had increased maximally at 13 days, and returned to normal at 21 days. Adrenal atrophy, however, was first noted at 10 days and adrenal weight continued to decline throughout the experimental period.