ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the effects of Rbl on action potentials and force of contraction in guinea pig ventricular papillary muscles.</p><p><b>METHOD</b>The ventricular papillary muscles of guinea pig were isolated regularly and immersed with Tyrode, s solution. The effects of Rbl (purified saponins of panaxnotoginseng) on the action potentials (AP), the slow action potentials and the force of contraction (FC) of the muscles were studied. The AP and FC were measured synchronously.</p><p><b>RESULT</b>Rbl shortened the duration of AP, including APD2O and APD90, and reduced the FC(n = 5, P < 0.01), but didn't affect the rest potential (RP), the amplitude of action potential (APA), overshot (OS) and maximal upstrok velocity (Vmax). Rbl also decreased the APA of slow action potential, but quinidine had no such effects.</p><p><b>CONCLUSION</b>Rbl may be a channel blocker.</p>