Effect of the total saponins of Panax notogiseng on contraction of rabbit aortic strips

The mechanism of vasodilator action of the total saponins of Panax notoginseng(PNS), which was noted in our preceeding work, was studied on isolated rabbit aortic strips. Norepinephrine(NE)-induced contraction response was antagonized by 2*10(-4) and 6*10(-4) g/mL PNS in a non-competitive manner. In Ca++-free Krebs solution, NE only caused initial fast response, which was not influenced by PNS. Ca++-dependant response after addition of Ca++(2.5 mM) was markedly reduced by 6*10(-4) g/mL PNS.In contrast, PNS did not antagonize KCl-induced contraction response. The results indicate that PNS is probably a calcium entryblocker which causes vasodilation by inhibiting adrenoceptor-operated calcium influx.