Fig. 15.

Increasing the FM1–43 concentration facilitates spontaneous entry. A cell was permeabilized with ionomycin and superfused with a saline buffered to contain 100 nmCa²⁺. After a control period, 5 and then 40 μm FM1–43 were added. Upper trace, Total fluorescence measured in sequential images of the terminal plotted as a function of time. Lower trace, Normalized fluorescence plotted as a function of time. The fluorescence in the surface membrane and that in the cytoplasm (multiplied by the geometric factor ρ) were summed, normalized by the dye concentration, and then scaled so that the normalized fluorescence in the surface membrane had a value of 1.