EFFECT OF LIDOCAINE ON ACTION POTENTIALS, CURRENTS AND CONTRACTIONS IN THE ABSENCE AND PRESENCE OF OUABAIN IN GUINEA-PIG VENTRICULAR CELLS

¹ Department of Physiology, Marischal College, University of Aberdeen, Aberdeen AB9 1AS

The effects of lidocaine have been investigated on electrical and contractile activity in guinea-pig ventricular cells in the absence and in the presence of ouabain. At low (therapeutic) doses, lidocaine induced a small reduction in action potential duration and contraction but had no effect on transient depolarizations or, under voltage-clamp conditions, on the transient inward currents. At much higher concentrations of lidocaine ( 500 µM), where the fast inward sodium current was substantially blocked, there was also a marked reduction in the amplitude of the calcium current and accompanying phasic contraction. Again, lidocaine did not inhibit the transient depolarizations or transient inward currents. This suggests that there is no direct effect of lidocaine on the calcium-induced release of calcium from the sarcoplasmic reticulum and that lidocaine does not indirectly inhibit arrhythmic activity by reducing intracellular sodium in the isolated ventricular cell. Possible mechanisms for the antiarrhythmic action of lidocaine in whole heart are discussed.

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