Effect of Drugs Related toα-Ethyltryptamine on Stress-Induced ACTH Secretion in the Dog

Abstract

To investigate the mechanismby which or ethyltryptamine inhibits ACTH secretion in stressed dogs, we determined the effects on adrenal secretion of a variety of related drugs. Alpha-methyltryptamine inhibited ACTH secretion as effectively as a-ethyltryptamine. Tryptamine, tryptophan, 5-hydroxytryptamine and 5-hydroxytryptophan did not inhibit ACTH secretion, suggesting that indole structure is not related to inhibition. Iproniazid and pargyline, 2 monoamine oxidase inhibitors, and imi-pramine and amitriptyline, 2 antidepressants which do not inhibit monoamine oxidase, also failed to inhibit ACTH secretion. Tranylcy-promine, a monoamine oxidase inhibitor and antidepressant, inhibited the adrenocortical response to ACTH. The pressor amines, amphetamine and methamphetamine, inhibited ACTH secretion, but, in general, they had this effect only when they produced marked, prolonged pressor responses. Alpha-ethyltryptamine itself often did not block ACTH secretion if it failed to produce a marked pressor response. It appears that the ACTH-inhibiting activity of [alpha]-ethyltryptamine is correlated with its pressor activity.