Comparative physiology of the vasomotor effects of neurohypophysial peptides in the Vertebrates

Abstract

The neurohypophysial peptides are vasopressor or depressor in action depending on the species. Isotocin, mesotocin and oxytocin constrict the branchial vessels in fish and induce a reflex vasodilation in the systemic vasculature. The vasodilation has persisted in some higher vertebrates and is particularly prominent in the snakes and birds where vasotocin and arginine vasopressin also are vasodepressor but are much less potent than mesotocin and oxytocin. In other vertebrates including fish, vasotocin and vasopressin are pressor and exert their effects mainly on the peripheral resistance. The newt, toads and soft-shell turtle gave pressor responses to all neurohypophysial peptides, with vasotocin showing the highest potency. The frogs, big-headed turtle and lizards were intermediate with vasotocin being pressor, mesotocin being pressor and oxytocin exhibiting a dual effect. © 1977 American Society of Zoologists.