Effects of Panax notoginseng saponins on cardiac action potentials and slow inward current

The effects of total saponins of Panax notoginseng (PNS) on contraction force, normal and slow response action potentials and slow inward current of guinea pig papillary muscles were studied by intracellular microelectrodes and voltage clamp techniques. The contraction force was decreased and the APD20, APD90 of normal AP were shortened in the presence of PNS 1 mg/ml, while the RP, APA and Vmax remained unchanged. The APA of slow AP induced with high K+ was decreased to 85% of its normal value after 20 min of perfusion with PNS solution. Isi was decreased from a peak value of 9.8 +/- 2.0 to effects of PNS on slow affecting INa. The 6.9 +/- 3.6 microA without AP and Isi were reversed by increasing calcium concentration. The results indicate that PNS has a selective blocking effect on calcium channels.