DESMOPRESSIN-INDUCED DOG CILIARY ARTERY RELAXATION

In isolated dog posterior ciliary arteries contracted with prostagland in F-2 alpha, desmopressin (10(-10) to 10(-8) M), a vasopressin V-2 re ceptor agonist. produced a concentration-related relaxation, which was reversed to a contraction by removal of the endothelium. Desmopressin was approximate 1/100 as potent as arginine vasopressin. Treatment wi th N-G-nitro-L-arginine. a nitric oxide (NO) synthase inhibitor, rever sed the desmopressin-induced relaxation to a contraction and the addit ion of L-arginine restored the relaxation. SR4905Y -1H-indole-2-carbon yl]-pyrrolidine-2-carboxamide), a selective vasopressin V-1 receptor a ntagonist, suppressed the relaxation. In endothelium-denuded arteries, desmopressin-induced contractions were also inhibited by SR49059. It is concluded that desmopressin, although much less potent than vasopre ssin, relaxes ciliary arteries via a mediation of NO synthesized from L-arginine in the endothelium. Vasopressin V-1-receptor subtypes appea r to be involved in the desmopressin-induced relaxation and contractio n. (C) 1998 Elsevier Science B.V.