Objective: To investigate the effect of Cyclovirobuxine D(CVB-D) on action potentials in isolated guinea pig ventricular myocytes. Methods: The single myocytes were enzymatically obtained from the guinea pig hearts and the action potentials were examined by whole-cell patchclamp technique. Results: 4×10-4 g/L CVB-D decreased action potential amptitude(APA)from 113.3±6.3 mV to 110.2±6.4 mV(n=6

P<0.01)

prolonged action potential duration of repolarization 50%(APD50)from 616.3±68.0 ms to 657.4±79.5 ms(n=6

P<0.01)

prolonged action potential duration of repolarization 90%(APD90)from 633.5±71.2 ms to 669.2±74.4 ms(n=6

P<0.01)

Prolonged action potential duration of repolarization 50% to repolarization 90%(APD50-90)from 15.9±6.0 ms to 20.1±5.2 ms(n=6

P<0.01)

and decreased decay slope of phase 3 (V3) from -2.6±0.8 V/s to -2.4±0.7 V/s(n=6

P<0.01).Compared with the baseline

4×10-3 g/L CVB-D makes the APD50-90 pass to increase trend gradually

but the variety trend of the V3 decrease gradually

other index sign varieties are consistent. Conclusion: CVB-D decreased APA and V3

and prolonged APD50

APD90

APD50-90

which may be its mechanism of positive inotropic effect and antiarrhythmic effect.