Involvement of Vasopressin in Histamine- and Stress-Induced Prolactin Release: Permissive, Mediating or Potentiating Role?

Abstract

Arginine vasopressin (AVP) appears to be involved in the histamine (HA)- and stress-induced prolactin (PRL) release. The present investigation was performed in male rats to clarify whether the role of AVP in HA- and restraint stress-induced secretion of PRL is mediating (i.e., the effect of HA or stress is transmitted via AVP) or permissive (i.e., the presence of AVP is required to obtain a stimulatory effect of HA or stress on PRL secretion). Furthermore, we studied whether AVP possessed a potentiating effect on the HA- or stress-induced PRL release. PRL secretion was stimulated 14- to 17-fold by intracerebroventricular infusion of HA (270 nmol) or by 5 min of restraint stress. These effects were inhibited about 80% by immunoneutralization of endogenous AVP with a specific AVP antiserum (abAVP). When specific AVP V1- or V2-receptor agonists, which were not bound by the AVP antiserum, were administered intravenously together with the AVP antiserum, the PRL response to HA or restraint stress was partly (> 50%) reestablished. This effect was observed at low (1.2 or 0.1 nmol) as well as high (3.8 or 0.4 nmol) doses of agonists and when these were administered alone or in combination. In non-immunoneutralized animals, separate administration of agonists at low or high doses as well as combined administration of agonists at low doses had no or only a minor effect on PRL secretion, while combined administration of V1- and V2-agonist in high doses stimulated PRL secretion 6-fold. Taken together, these observations indicate that AVP has a permissive role.(ABSTRACT TRUNCATED AT 250 WORDS)