Fig 3.

Stimulus-evoked reorganization of filaments after microinjection of phalloidin. (A–C) Electron micrographs from two different synapses in axons that were microinjected with phalloidin and then stimulated at 5 Hz for 30 (A and B) and 15 min (C), respectively, before fixation. Synaptic vesicles (open arrows) are tethered along filaments (thin arrows) extending from the endocytic zone toward the margin of the vesicle cluster. (D and E) Sections from a different synapse in the same specimen as in C. Many clathrin-coated pits (ccp), some of which had an elongated neck, occurred at the plasma membrane of the endocytic zone. Actin-like filaments attached to the neck of coated pits are indicated by thin arrows. Other designations are as in Fig. 2. (Bars: A, 0.5 μm; B–E, 0.2 μm.)