Potentiation by Vasopressin of Corticotropin Release Induced by Corticotropin-Releasing Factor1

Abstract

To determine whether vasopressin affects the sensitivity of the anterior pituitary to corticotropin-releasing factor, vasopressin was administered intravenously in doses subthreshold with respect to ACTH release to rats pretreated with dexamethasone (dex), Nembutal (Nem), and, sometimes, also morphine (morph). Crude ovine CRF was given intravenously immediately following the vasopressin. The adrenocortical response to CRF was increased at least 100% by the prior administration of subthreshold doses of vasopressin. When 1/20 of the intravenous dose of vasopressin was placed into both lobes of the anterior pituitary it again failed to release ACTH itself, but increased 2.5 times the response to CRF given intravenously. This potentiation of CRF-induced ACTH release by vasopressin at the adenohypophysis was not observed if the vasopressin was administered into one lobe only of the anterior pituitary. In rats pretreated with dex +Nem the potentiation was the same as in those pretreated with dex + Nem+morph. Ox...