[Effect of a diethylamino analog of ethmozine on the force of contraction and action potential of the guinea pig myocardium].

Ethacizine applied in the concentration range between 1 X 10(-7) and 1 X 10(-5) g/ml decreased the rate of action potential growth (Vmax) of the mammal myocardium. Inhibition of the Vmax was accompanied by the diminution of the force of contraction which involved two phases. Ethacizine also decreased the overshoot of slow response action potential with the time constant similar to that in the first rapid phase of force reduction. It is assumed that the first rapid phase occurred due to the blockade of the slow calcium channels, while the second slow phase resulted from the inhibition of Na--Ca exchange because of the decrease of intracellular Na+ concentration after the blockade of the fast sodium channels by ethacizine.