Fig. 4.

Time course of SV retrieval. The bar histogram shows the percentage of recycled membrane at different time points. The percentage of recycled vesicle membrane was calculated as the percentage of labeled vesicle surface over the number of docked vesicles for each 3D reconstructed synapse at each time point. It appears that the membrane is labeled in two steps. The initial retrieval is at 4 s after stimulation. Between 10 and 20 s, labeled membrane doubles to the final amount of labeled vesicle membrane that equals the docked vesicle pool. Mean and SD are shown for each time point: 4 s, 58 ± 22%; 10 s, 49 ± 26%; 20 s, 96 ± 26%; 30 s, 85 ± 42%. The means between 10 and 20 s are statistically different (P < 0.01).