Nitric oxide hyperpolarizes arterial smooth muscle

Abstract

The actions of nitric oxide (NO) on the membrane potential of vascular smooth muscle were investigated using segments of guinea pig uterine arteries that were depolarized and constricted with phenylephrine. Exogenous NO (4 x 10-8 to 4 x 10-5 M) evoked concentration-dependent hyperpolarization and relaxation that were abolished following pretreatment of the arteries with hemoglobin and methylene blue. Nitroprusside and nitroglycerine also evoked hyperpolarization and relaxation of these arteries. Inhibitors of NO synthesis, N(G)-monomethyl-L-arginine and N(ω)-nitro-L-arginine methyl ester, reduced the hyperpolarization and relaxation induced by stimulation of the endothelium with acetylcholin..