Figure 5. Effect of Na⁺ channel blocker on action potential signals in ventricular muscles.

A healthy muscle was stimulated at 1 Hz by a pair of field electrodes placed at the end of the muscle, ∼2 mm distant from the field of view. A. Overlay of action potential signals from the whole field of view in the absence and presence of pilsicainide (0∼40 µM). B. Overlay of action potential signals in individual cells in the presence of 40 µM pilsicainide (cell 1∼3).