The Alpha-adrenoceptor Control of Adrenocorticotropin Secretion in Man

Oral administration to six normal male volunteers of an alpha-adrenoceptor agonist, guanfacine (4 mg daily for 4 days) had no significant effect on ACTH release induced by metyrapone (a single oral 1-g dose). The same treatment with guanifacine significantly reduced ACTH secretion stimulated by insulin-induced hypoglycemia in another group of six male volunteers. These results indicate that, in man, the adrenergic system has an inhibitory input on stress-induced ACTY secretion via alpha-adrenoceptors. The concept of alpha-adrenergic control of ACTH secretion in man is in agreement with some experimental in vivo and in vitro data recorded in animals.