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Figure 10.
Summary diagram of spontaneous SV fusion at larval zebrafish neuromuscular synapses. Three pools of SVs are depicted: resting pool, recycling pool, and RRP. In the early phase of TTX treatment (<1 h), spontaneous SV fusion is mobilized from the RRP with two distinct modes: virgin exocytosis with a slow time course (τ = 45 min at 25°C) and repeated reuse of the same SVs at a higher rate. The differences between the two modes of fusion are highlighted in the table at bottom. SVs equipped with both canonical and noncanonical v-SNAREs are involved in the two modes, although their dependency on the noncanonical v-SNARE is not identical. They may also be different in their coupling to the voltage-gated Ca2+ channels. SVs in RRP are intermixed with those in other pools after a prolonged (>1 h) TTX treatment.