Fig. 6

Bleb-induced spontaneous electrical activity (BIS). a Optical action potentials detected simultaneously from four different positions (p, and a–c). The optical action potential first appeared in trace p, indicating the site of the anomalous pacemaker. The arrowheads in trace p indicate the “pacemaker potential”-like diastolic depolarization. This event of BIS was observed 2 h after the application of Bleb (50 μM). b Optical mapping of the excitation spread. The excitatory wave spread toward the surrounding area from the anomalous pacemaker (open circle indicated by P). Other symbols are as defined in Figs. 1, 3, and 4