Quantitative analysis of vesicle recycling at the calyx of Held synapse

摘要: Vesicle recycling is pivotal for maintaining reliable synaptic signaling, but its basic properties remain poorly understood. Here, we developed an approach to quantitatively analyze the kinetics of vesicle recycling with exquisite signal and temporal resolution at the calyx of Held synapse. The combination of this electrophysiological approach with electron microscopy revealed that similar to 80% of vesicles (similar to 270,000 out of similar to 330,000) in the nerve terminal are involved in recycling. Under sustained stimulation, recycled vesicles start to be reused in tens of seconds when similar to 47% of the preserved vesicles in the recycling pool (RP) are depleted. The heterogeneity of vesicle recycling as well as two kinetic components of RP depletion revealed the existence of a replenishable pool of vesicles before the priming stage and led to a realistic kinetic model that assesses the size of the subpools of the RP. Thus, our study quantified the kinetics of vesicle recycling and kinetically dissected the whole vesicle pool in the calyceal terminal into the readily releasable pool (similar to 0.6%), the readily priming pool (similar to 46%), the premature pool (similar to 33%), and the resting pool (similar to 20%).