EFFECTS OF N-OMEGA-NITRO-L-ARGININE AND CAPSAICIN ON NEUROGENIC VASOMOTOR RESPONSES IN ISOLATED MESENTERIC-ARTERIES OF THE MONKEY

Monkey isolated mesenteric arterial rings denuded of endothelium const ricted upon transmural nerve stimulation (TNS) in the absence of activ e muscle tone. The constriction was potentiated by N-W-nitro-L-arginin e (3 x 10(-5)M), but not by the D-enantiomer (3 x 10(-5)M). The potent iation was reversed by L-arginine(3 x 10(-4)M). The neurogenic vasocon striction of mesenteric arteries was also augmented by capsaicin, but to a lesser extent than that induced by N-W-nitro-L-arginine. Indometh acin (10(-5)M) did not affect TNS-induced vasoconstriction. These find ings suggest that nerve-derived nitric oxide or a related substance ma y play a greater role than do capsaicin-sensitive vasodilator transmit ters in neurogenic regulation of mesenteric arterial tone in the monke y. The transmitter mechanisms for vasodilation in mesenteric circulati on vary among species.