Vasopressin receptor subtypes on mesenteric and cremasteric arterioles in rat

Abstract

We studied the effects of a selective vasopressin V 1A receptor antagonist [1-(1-(4-(3-acetylaminopropoxy)benzoyl)-4-piperidyl)-3,4-dihydro-2(1 H)-quinolinone (OPC-21268)] and a selective vasopressin V 2 receptor antagonist [5-dimethylamino-1(4-(2-methylbenzoylamino)benzoyl)-2,3,4,5-tetrahydro-1 H-benzazepine (OPC-31260)] on vasopressin-induced contraction of mesenteric and cremasteric arterioles in urethane-anaesthetized rats. Vasopressin was infused intravenously for 60 min or applied topically to arterioles directly. Vasopressin infusion (50, 100 or 500 ng/kg/min) decreased the diameter of both mesenteric and cremasteric arterioles. Vasopressin (500 ng/kg/min)-induced vasoconstriction was antagonized by OPC-21268 (0.2, 1.0 and 5.0 mg/kg, i.v.), dose-dependently, but not by OPC-31260. Topically applied vasopressin (4.6×10 −10–4.6×10 −8 M) dose-dependently constricted both microvessels. Pre-administration of OPC-21268 (5.0 mg/kg, i.v.) completely inhibited topically applied vasopressin-induced vasoconstriction in both microvessels, and OPC-31260 partially inhibited it in cremasteric arterioles. These results suggest that vasopressin induces vasoconstriction in rat mesenteric and cremasteric arterioles mainly by stimulating vasopressin V 1A receptors, while vasoconstriction in cremasteric arterioles is partly associated with stimulation of vasopressin V 2 receptors.