Aim: To study the effects of vinpocetine (Vin) on the sodium current (INa) in cardiomyocytes.
Methods: The sodium current in adult rat ventricular myocytes was measured by whole cell patch-clamp technique.
Results: The INa in cardiomyocytes was blocked reversibly by Vin, in concentration-dependent and voltage-dependent manner, but not rate- or use-dependent. The INa was attenuated by 13%-75% when the Vin concentration was raised from 10 to 80 mumol.L-1. The IC50 (95% confidence limits) was 36.4 (28.1-47.1) mumol.L-1. When the membrane potential depolarized over the range of -90 mV to +40 mV in 10-mV step, inhibitory effect of Vin on the INa was 39% at first, then maintained at a higher level, about 52% +/- 5%. The maximal depression (57%) reached at about 0 mV. Vin influenced both the activation and inactivation processes of sodium channel, and resulted in attenuation of the window currents (the slowly inactivating sodium currents).
Conclusion: Vin inhibited sodium currents in rat ventricular myocytes.