The membrane potential and smooth muscle tension in rat aorta were studied by the method of sucrose gap junction. It was found that sodium nitroprusside and nitroglycerin produced a dose-dependent membrane repolarization and smooth muscle cell relaxation in rat aorta preliminarily contracted and depolarized by hyperpotassium (40 mM) or phenylephrine solutions. The relaxation effect of sodium nitroprusside was more pronounced on the phenylephrine background. The effect of nitroglycerin showed a different kinetics in time and led to the tolerance development. The effects of both nitro compounds were inhibited by pretreatment with Methylene Blue or potassium channel blockers. It is suggested that nitro vasodilators are involved in the NO-dependent processes in smooth muscle cells of aorta through cGMP-mediated activation of the potassium conductivity and by changing the efficiency of operation of the protein kinase C branch of the Ca2+ signal system.