Extended Data Figure 6: Ultrafast endocytosis occurs with similar dynamics in 2 mM and 4 mM extracellular calcium.

a, A histogram showing the average number of action potentials at different time points before and after the light application in an external solution with 2 mM calcium. Each column is binned by 10 ms. Action potentials observed after light-off are probably due to spontaneous activity of cells. b, Average number of action potentials triggered during the 10 ms light pulse. An action potential was observed during the light pulse in 73% of the cells (11/15); 13% (2/15) fired a second action potential within the 10 ms light pulse. No action potential was observed in 27% of the cells (4/15). c–e, Representative micrographs showing invaginations and large vesicles in the periactive zone at 100 ms after stimulation. f, g, Average number of exocytic pits (f) and endocytic structures (g) at 0 ms (no stim), 30 ms and 100 ms after stimulation in 2 mM calcium (light grey) and in 4 mM calcium (dark grey) conditions. Endocytic structures include shallow and deep pits summed. 4 mM data are from the samples in Figs 1 and 3. Error bars, s.e.m.