Angiotensin Stimulation of Vasopressin Release from the Rat Hypothalamo-Neurohypophyseal System in Organ Culture*

Abstract

Angiotensin II (All) stimulated vasopressin (VP) release from the rat hypothalamo-neurohypophyseal system (HNS) in organ culture in a concentration-dependent manner. Exposure to All at 10^-8 M for 1 h yielded a 1.8-fold increase in VP release over control release (P < 0.01), while a 1-h exposure to 10^-5 M All resulted in a 4-fold increment over control VP release by HNS explants maintained in organ culture for 3 days (P < 0.01). Saralasin, an All antagonist, blocked All stimulation of VP release without significantly altering basal VP release by the HNS explants. Saralasin did not interfere with stimulation of VP release by acetylcholine or nicotine. Tetrodotoxin (10^-7g/ml) also blocked All stimulation of VP release. These findings suggest that action potentials are generated in response to All stimulation of specific receptors in the HNS and are requisite for VP release in response to this stimulus.