Electron microscopy of synaptic vesicles labeled with C2-XL-HRP
(A and B) Representative electron micrographs of terminals loaded with 4 μM C2-XL-HRP by high K+ stimulation followed with (B) or without (A) a 1-min EGTA wash step. Post-stimulation recovery time was 10–20 min. Arrows indicate endosome-like vacuoles.
(C) Distributions of vesicle diameters in terminals loaded with C2-XL-HRP by high K+ stimulation. Black bars, C2-positive vesicles (n = 359); white bars, C2-negative vesicles (n = 783).
(D) Distributions of vesicle diameters in terminals loaded by spontaneous activity (overnight incubation with C2-XL-HRP). Black bars, C2-positive vesicles (n = 199); white bars, C2-negative vesicles (n = 492).