Figure 12.

Previously immobilized vesicles advanced a short distance toward the membrane just before fusion. A, In a rod that was voltage clamped at −70 mV and then depolarized to −10 mV, a previously immobilized vesicle (a) loaded with dextran-conjugated pHrodo showed a small brightening (b) just before fusion (c) in response to a depolarizing stimulation. B, Fluorescence intensities were plotted against time for the vesicle shown in A. Images in A were obtained at the time points marked a–c. C, Relative fluorescence profiles averaged from five vesicles in three rods and normalized to their peak intensity values. Scale bar, 0.5 μm.