The V1b neurohypophysial peptide receptor in fish and rat pituitary

In Mammals, arginine vasopressin (AVP) and oxytocin (OT) exert a corticotrophin releasing factor (CRF)-like effect on adrenocorticotrophin hormone (ACTH) release. A similar effect exists in trout pituitary in the presence of arginine vasotocin (AVT) or isotocin (IT). The present data, showing the vasopressin V-1 analogues to be more efficient than V-2, support the presence in trout pituitary of an AVT-receptor pharmacologically close to the mammalian V1b-type. In rat pituitary, AVT and IT were as efficient as CRF on ACTH release. They were more efficient than AVP or OT on cAMP production (when combined with CRF) and on intracellular Ca2+ mobilization. Results with specific analogues favoured the presence of a V1b receptor. Interestingly, the combination of AVT with the antagonists should permit to characterize better the V1b receptor. These results revealed a peculiar pharmacological profile of the neurohypophysial peptide receptor involved in the control of ACTH release in the pituitary.