Influence of Apamin on the Extracellularly Recorded Action Potentials Profiles of Subepicardial Cardiomyocytes of the Rat Heart in Myocardial Infarction

The role of small-conductance Ca²⁺-activatedK⁺-channels (SK channels) in the pathogenesisof cardiomyopathies of various etiologies remains poorly understood.The purpose of this work was to evaluate the effect of the blockerof SK channels, apamin, on the extracellularly recorded action potentials(eAPs) of subepicardial myocytes in the left ventricles of sham-operatedrats and rats with myocardial infarction caused by ischemia-reperfusion.It was found that local delivery of the SK channel blocker apaminat a concentration of 500 nM to the eAP recording area did not affectthe eAP profiles in the group of sham-operated rats but caused asignificant slowdown in the repolarization time and a decrease inthe afterhyperpolarization phase of eAPs in the group of rats withmyocardial infarction. These data suggest that changes in the waveformof eAPs after infarction are associated with increased expressionand/or activity of SK channels in subepicardial myocytes. The possiblerole of these channels in the structural and functional remodelingof the myocardium of the left ventricle of the heart after ischemia-reperfusionis discussed.