Figure 3. Bulk endocytosis and conversion of bulk endosomes into SVs analyzed with soluble HRP labeling after high K+ stimulation in WT and dynamin mutant synapses.
Neurons of the indicated genotypes (A, WT and Dyn1 KO; B, Dyn3 KO and Dyn1/3 DKO respectively) were stimulated with 90 mM K+ for 90 s in the presence of HRP, followed by wash-out of HRP and recovery in resting buffer. Massive bulk endocytosis is observed during stimulation. The large fraction of HRP reaction product-positive SVs observed in all genotypes during the recovery period documents formation of these vesicles from HRP reaction product-positive bulk endosomes formed during stimulation. Scale bar = 500 nm.