Extracellular Action Potentials of Ventricular Cardiomyocytes in the Heart Isolated From Rats Kept on a High-Fat/High-Sucrose Diet

Rats kept on a high-fat/high-sucrose diet (HFSD) for 10–12weeks demonstrated the development of hyperglycemia and signs ofvisceral obesity. Compared to the control, extracellular actionpotentials (eAP) of subepicardial myocytes of the left ventricle(LV) of HFSD rats characterized by a significantly increased fractionof signals with a pronounced afterhyperpolarization (AHP) phaseand an accelerated decline. Local delivery of apamin (a blockerof small conductance Ca²⁺-activated K⁺ channels(IK_Ca, SK channels) to the eAP registrationcite at a concentration of 500 nM in the solution inside the pipette wasaccompanied by suppression of the AHP phase and prolongation ofthe eAP decline. The obtained data suggest that HFSD leads to anincrease in the expression and/or activity of SK channels and, asa result, to the development of AHP and shortening of eAP in epicardialcardiomyocytes of the LV of the rat heart.