Permissive, mediating and potentiating effects of vasopressin in the ACTH and beta-endorphin response to histamine and restraint stress.

Abstract

We investigated in conscious, male rats (1) whether the role of arginine-vasopressin (AVP) in histamine (HA)- and/or restraint stress-induced stimulation of ACTH and beta-endorphin (beta-END) secretion is mediating and/or permissive and (2) whether AVP possesses a potentiating effect on HA- or stress-induced release of ACTH and beta-END. Administration of a specific V1 receptor agonist stimulated ACTH and beta-END secretion dose-dependently while a V2 receptor agonist had no stimulating effect. ACTH and beta-END secretion was stimulated 2- to 3-fold by intracerebroventricular (i.c.v.) infusion of HA (270 nmol) or by 5 min of restraint stress. These effects were inhibited approximately 80% by immunoneutralization of endogenous AVP using a specific AVP antiserum. When the 'AVP tone' was restored in immunoneutralized animals by administration of the specific AVP V1 receptor agonist, which was not bound by the AVP antiserum and had no ACTH and beta-END-releasing effect in the dose used, the ACTH and beta-END response to HA or restraint stress was almost completely reestablished. The specific AVP V2 receptor agonist, which was not bound by the AVP antiserum, reestablished only in part the response of ACTH and beta-END to HA or restraint stress in immunoneutralized animals. AVP administered in doses which had no or minimal ACTH or beta-END releasing effect in itself enhanced the ACTH or beta-END response to submaximal stimulation with HA or restraint stress.(ABSTRACT TRUNCATED AT 250 WORDS)