Fig. 1

Effect of mild hypokalemia on wild-type (WT) mouse myocytes. a Hyperpolarization of the resting membrane potential (RMP) of WT mouse myocytes. As indicated by the blue bar, the bathing solution was switched from the 5.4 mM extracellular potassium (K⁺) concentration ([K⁺]_o) solution to the 3 mM [K⁺]_o solution. b The induced action potention (AP) in the 5.4 mM [K⁺]_o solution (blue line) and the 3 mM [K⁺]_o solution (black line). c The AP recorded in the same myocytes as those mentioned in b (the black line, control; the red line, in the presence of 10 μM ivabradine [IVA]). The K⁺ concentration of the bathing solution was 3 mM. The dotted line indicates 0 mV (color figure online)