INHIBITORY EFFECTS OF VINPOCETINE ON SODIUM CURRENT IN RAT CARDIOMYOCYTES

AIM: To study the effects of vinpocetine (Vin) on the sodium current ( I-Na) in cardiomyocytes. METHODS: The sodium current in adult rat vent ricular myocytes was measured by whole cell patch-clamp technique. RES ULTS: The I-Na in cardiomyocytes was blocked reversibly by Vin, in con centration-dependent and voltage-dependent manner, but not rate or use -dependent. The I-Na was attenuated by 13 % - 75 % when the Vin concen tration was raised from 10 to 80 mu mol . L-1. The IC50(95 % confidenc e limits) was 36.4 (28.1 - 47.1) mu mol . L-1. When the membrane poten tial depolarized over the range of -90 mV to + 40 mV in 10-mV step, in hibitory effect of Vin on the I-Na was 39 % at first, then maintained at a higher level, about 52 % +/- 5 %. The maximal depression (57 %) r eached at about 0 mV. Vin influenced both the activation and inactivat ion processes of sodium channel, and resulted in attenuation of the wi ndow currents (the slowly inactivating sodium currents). CONCLUSION: V in inhibited sodium currents in rat ventricular myocytes.