Positive Feedback of Vasopressin on its Own Release in the Central Nervous System: in vitro Studies

Abstract In this paper evidence is shown that synthetic arginine vasopressin (AVP) can evoke marked in vitro release of endogenous immunoreactive AVP (I-AVP) from male rat septal and hypothalamic tissue superfused in vitro. The stimulatory action was dosedependent with a maximal amplification factor of 2.3 when using 14 pg of synthetic AVP as the stimulus. It was highly specific since only AVP was effective and not three closely related substances such as lysine vasopressin, oxytocin and a 4-9 C fragment of AVP. This reproducible effect of AVP required, however, effective concentrations of bacitracin (10(-4) to 10(-5) M) in the superfusion medium to inhibit aminopeptidase(s) capable of inactivating AVP. Lastly, the stimulatory action of AVP on its own release was not blocked by a V(1)-receptor antagonist of AVP but was blocked by a V(2)-antagonist. It is proposed that this novel and robust positive feedback of AVP on its own release may be involved in the mechanism of memory consolidation of certain behavioral tasks known to be affected by AVP.