V1 receptor in ENS mediates the excitatory effect of vasopressin on circular muscle strips of gastric body in vitro in rats.

The purpose of this study was to localize vasopressin (VP) V(1a) receptor in stomach and to characterize the role of VP in the regulation of gastric motility in rats. Double staining was used to locate the V(1a) receptor in the gastric body of the rat. The contraction of the circular muscle strips of gastric body was monitored by a polygraph. V(1a) receptor was expressed on the neurons of myenteric plexus of the gastric body. VP (10(-10)-10(-6) M) caused a concentration-dependent contractile effect on the circular muscle strips of gastric body in vitro. V-1880 ([deamino-Pen(1), O-Me-Tyr(2), Arg(8)]-Vasopressin, 10(-7) M), a V(1) receptor antagonist, inhibited the spontaneous contraction of the strips. Tetradotoxin (TTX, 10(-6) M) and V-1880 (10(-7) M) abolished the excitatory effect of VP. Atropine (10(-6) M) partially inhibited VP-induced excitatory effect on the muscle strips but hexamethonium (10(-4) M) did not influence it. These results suggest that V(1a) receptor was expressed on the neurons of myenteric nerves. The cholinergic nerve was involved in the excitatory effect of VP on the contraction of gastric body.