Figure 10.

Mild stimulation evokes a specific single SV endocytosis pathway independent of cdk5 activity. A, Cultures were stimulated twice for 10 s with two trains of 400 action potentials (40 Hz), repolarized for 10 min, and then stimulated again with a train of 200 action potentials (10 Hz) in the presence of HRP. HRP was kept present for an additional 60 s to ensure labeling of all retrieval pathways and then cultures were fixed. Cultures were preincubated with 50 μm roscovitine (Rosco) for 10 min before the first stimulations and at all steps up to fixation where indicated. B–G, Representative electron micrographs of HRP uptake in control (B–D) or roscovitine-treated (E–G) nerve terminals. Scale bars, 200 nm. Five roscovitine nerve terminals were discounted because they had an atypical number of HRP endosomes compared with the rest (total = 57). H, Mean number of HRP-labeled structures per nerve terminal for either control (open bars) or roscovitine treated (gray bars) cultures ± SEM (Ctrl, n = 29; Rosco, n = 51; *p < 0.05, Student's t test).