Abstract: AIM: To study the selective vasodilating action in small artery and its pharmacological mechanisms of the novel antihypertensive drug iptakalim hydrochloride (Ipt).METHODS: Differences of the vasodilating action of Ipt in big artery and small artery were studied using isolated rat tail artery helical strips and aortic rings, and the effects of Ipt on potassium currents in smooth muscle cells derived from rat tail artery were observed by using patch clamp technique.RESULTS: The vasodilating action of Ipt at 10^-7-10^-3 mol·L^-1 was observed in rat tail artery strips precontracted with potassium chloride (KCl) in a concentration-dependent manner, and the vasodilating action presented a partially endothelium-dependent character, but no significantly vasodilating effect was seen in rat aortic rings.Ipt-induced relaxation in tail artery was significantly greater in spontaneously hypertensive rat than that in normotensive rat, and the vasodilating action of Ipt in small artery could be markedly antagonized by glibenclamide (10 μmol·L^-1) which only inhibited ATP-sensitive potassium channels.Moreover, the potassium currents in smooth muscle cells derived from rat tail artery could be augmented by Ipt.CONCLUTION: The novel antihypertensive drug iptakalim hydrochloride has a selective vasodilating action in small artery, and it has major pharmacological characters of ATP-sensitive potassium channel openers.

Key words: iptakalim hydrochloride, ATP-sensitive potassium channel openers, rat tail artery, rat aorta, potassium currents