Depressant actions of Panax notoginseng saponins on vascular smooth muscles

Effects of total saponins of Panax notoginseng (PNS) and purified saponins Rgl. Re and Rbl, from Panax notoginseng on cardiovascular system were studied in vivo (cats) and in vitro (various isolated rabbit vascular strips). In urethane anesthetized cats. mean blood pressure. mesenteric and renal arterial resistance fell after iv PNS 25-100 mg/kg. meanwhile. mesenteric arterial blood flow increased but no change in heart rate. PNS was more potent in dilating the mesentcric artery than renal artery. In various isolated rabbit vascular spiral strips, PNS l-3 mg/ml had no influence on the resring tension and beta2-adrenoceptor reactivity, but the contractions induced by KCl+ CaC12, KCI or norepinephrine (NE) were inhibited non-competitively. Furthermore. PNS, like verapamil (Ver). tended to be more effective in inhibiting contraction induced by KCl+ CaC12 or KCI than that by NE and more effective in inhibiting contraction of mesenteric artery. femoral artery, renal artery. inferior vena cava and portal vein than that of aorta and pulmonary artery. Also. PNS 1 mg/ml markedly inhibited the spontaneous contractile activity in portal vein. In the experiment of NE-induced 2-component contraction of aorta, Rg1 and Re inhibited the initial fast non-sustained component of response and Rb, inhibited the slow Ca0-dependent component of contraction selectively, while PNS. similar to Ver, inhibited both components. The results indicate that the vasodilation effect of PNS is vascular selective. PNS is probably a calcium channel blocker like Ver. It was further proved that intracellular Ca2+ release was inhibited by Rgl and Re and extraccllular Ca2+ influx was blocked by Rbl.