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 10–12 weeks demonstrated the development of hyperglycemia and signs of visceral obesity. Compared to the control, extracellular action potentials (eAP) of subepicardial myocytes of the left ventricle (LV) of HFSD rats characterized by a significantly increased fraction of signals with a pronounced afterhyperpolarization (AHP) phase and an accelerated decline. Local delivery of apamin (a blocker of small conductance Ca2+-activated K+ channels (IKCa, SK channels) to the eAP registration cite at a concentration of 500 nM in the solution inside the pipette was accompanied by suppression of the AHP phase and prolongation of the eAP decline. The obtained data suggest that HFSD leads to an increase in the expression and/or activity of SK channels and, as a result, to the development of AHP and shortening of eAP in epicardial cardiomyocytes of the LV of the rat heart.