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Updated: Sep 30, 2026

FM Dye Cycling at the Synapse: Comparing High Potassium Depolarization, Electrical and Channelrhodopsin Stimulation
Published on: May 24, 2018
Selective replenishment of two vesicle pools depends on the source of Ca2+ at the Drosophila synapse
Hiroshi Kuromi1, Yoshiaki Kidokoro
1Institute for Behavioral Sciences, Gunma University School of Medicine, 3-39-22 Showa-machi, Maebashi, Japan. kuromi@med.gunma-u.ac.jp
Abstract:
After synaptic vesicles (SVs) undergo exocytosis, SV pools are replenished by recycling SVs at nerve terminals. At Drosophila neuromuscular synapses, there are two distinct SV pools (i.e., the exo/endo cycling pool (ECP), which primarily maintains synaptic transmission, and the reserve pool (RP), which participates in synaptic transmission only during tetanic stimulation). Labeling endocytosed vesicular structures with a fluorescent styryl dye, FM1-43, and measuring intracellular Ca2+ concentrations with a Ca2+ indicator, rhod-2, we show here that the ECP is replenished by SVs endocytosed during stimulation, and this process depends on external Ca2+. In contrast, the RP is refilled after cessation of tetanus by a process mediated by Ca2+ released from internal stores.
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