Apparent calcium dependence of vesicle recruitment

摘要

Key points class="unordered" style="list-style-type:disc" id="tjp13118-list-0001">Synaptic transmission relies on the recruitment of neurotransmitter‐filled vesicles to presynaptic release sites. Increased intracellular calcium buffering slows the recovery from synaptic depression, suggesting that vesicle recruitment is a calcium‐dependent process.However, the molecular mechanisms of vesicle recruitment have only been investigated at some synapses.We investigate the role of calcium in vesicle recruitment at the cerebellar mossy fibre to granule cell synapse. We find that increased intracellular calcium buffering slows the recovery from depression following physiological stimulation. However, the recovery is largely resistant to perturbation of the molecular pathways previously shown to mediate calcium‐dependent vesicle recruitment.Furthermore, we find two pools of vesicles with different recruitment speeds and show that models incorporating two pools of vesicles with different calcium‐independent recruitment rates can explain our data. In this framework, increased calcium buffering prevents the release of intrinsically fast‐recruited vesicles but does not change the vesicle recruitment rates themselves.