Synchronous and asynchronous fusion events. (A) Light intensity change as a function of time for the synchronous and asynchronous fusion events indicated in Fig. 1 C (white and red arrows, respectively). The dotted line indicates the differences in peak amplitudes between the two types of events. (B) Example of the submembranous [Ca²⁺] measured in a cell loaded with 0.2 mM Fluo-5N through the patch pipette. Calcium currents were evoked by four 90-ms depolarization steps delivered at 200-ms intervals. The plot below shows the submembranous [Ca²⁺] averaged over the whole footprint in a given cell. Similar results were seen for seven other cells. The upper plot shows cumulative exocytosis of synchronous (black) and asynchronous (red) events measured by IRM in response to the same stimulus (n = 10 cells).