Small endocytic vesicle hot-spots at dorsal ridges of the growth cone. (A-B) Time-lapse confocal images of FM 5-95 internalization show numerous small endocytic vesicles that form at dye-labeled dorsal ridges of the growth cone. For each example (A-B), the frame showing initial membrane labeling immediately following the focal dye pulse is shown at the left (0:01). The boxed regions (left panels) are shown at higher magnification in the right panels. Time, following the initial membrane labeling, is indicated for each frame in minutes:seconds. In each example, the peripheral filopodia are slightly below the dorsal focal plane in the confocal section. Note the radial progression (inside-out) of endocytic vesicle formation, which is indicated by the yellow arrowheads marking nascent vesicles. Time-lapse movies are shown in Additional file 1. Scale bars, 5 μm (left), 1 μm (right).