RELEASE OF VASOPRESSIN FROM THE SEPTUM AND HIPPOCAMPUS OF FREELY BEHAVING MALE-RATS - EFFECT OF BACITRACIN AND SYNTHETIC VASOPRESSIN

This paper describes the release characteristics of arginine vasopressin (AVP) from the dorsal septum and dorsal hippocampus of freely behaving male rats using miniaturized push‐pull cannulae and a slow rate of perfusion to minimize tissue damage. The major findings were that) The spontaneous release of immunoreactive AVP (l‐AVP) from the dorsal hippocampus was episodic in nature and did not require the presence of bacitracin in the perfusion medium to reliably demonstrate its pattern of release; 2) despite the fact that the septum has close to seven times more I‐AVP per/mg of tissue, the dorsal septum perfusates had undetectable levels of the neuropeptide; 3) under these conditions hypertonic saline intraperitoneally did not alter the spontaneous release of this peptide; and 4) only when the perfusion medium contained effective concentrations of bacitracin (10−4 M) were reliable and detectable levels of I‐AVP measured in perfusates from the dorsal septum and exogenous synthetic AVP had a robust positive feedback action on its own release. The physiological relevance and importance of this robust and novel effect of AVP remains to be elucidated. Copyright © 1990, Wiley Blackwell. All rights reserved