ABSTRACT
Abstract 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.
