THE ROLE OF CENTRAL CORTICOLIBERIN IN THE HYPEROSMOSIS-INDUCED SECRETION OF NEUROHYPOPHYSEAL HORMONES AND CORTICOSTERONE IN THE RAT

Although synthetic corticotropin-releasing hormone (CRH) is known to i nfluence the secretion of the neurohypophysial hormones, the role of e ndogenous CRH in the rat brain is still unclear in this respect. Accor dingly, experiments were scheduled to study the effects of intracerebr oventricularly (i.c.v.) administered CRH-antiserum (AS) on the hyperos mosis-induced secretion of arginine-8-vasopressin (AVP), oxytocin (OXT ) and corticosterone in Wistar male rats. A 2 mu l CRH-AS injection wa s given, and repeated 24 h later, 30 min prior to intraperitoneal admi nistration of hypertonic saline (HS; 2.5% NaCl, 2 ml/100 g body weight ) followed by decapitation in 15 min. Plasma AVP and OXT were measured by radioimmunoassay and corticosterone by fluorimetry. HS increased t he levels of AVP, OXT and corticosterone. CRH-AS did not change the pl asma concentrations of these hormones in 0.9% NaCl-treated animals. CR H-AS pretreatment prevented the corticosterone-releasing action of HS, and significantly moderated the HS-induced AVP and OXT increase. Thes e findings suggest that the central CRH system may participate in the regulation of corticosterone and neurohypophysial hormone secretion ev oked by acute osmotic challenge.