[Effect of nonachlazine on transmembrane ionic currents in the frog atrial trabeculae]

The effect of the antianginal drug nonachlazine displaying antiarrhythmic properties on transmembrane ionic currents in the frog atrial fibers was studied in experiments on isolated trabeculae of the frog atria. The transmembrane ionic currents were measured by a voltage clamp technique based on a double sucrose gap arrangement. Nonachlazine (1.03 X 10(-5) mol/l) decreased the amplitude of the fast inward current whatever the magnitude of membrane potential. The drug inhibited the slow inward current and prevented the adrenaline-increased permeability of the slow sodium-calcium channel if external sodium ions were replaced by choline chloride. Nonachlazine (1.03 X 10(-5) mol/l) diminished the amplitude of the inward ionic current in a calcium-free medium as well. The stimulatory effect of prostacycline (2 X 10(-7) mol/l) on the fast inward ionic current was inhibited by nonachlazine. The data obtained suggest that the antiarrhythmic effect of nonachlazine might be linked with the inhibition of the fast sodium inward current and the slow calcium inward current.