Full simulation on the dynamics of auditory synaptic fusion: Strong clustering of calcium channel might be the origin of the coherent release in the auditory hair cells

The precise timing of synaptic transmission in auditory hair cells is important to hearing and speech recognition. Neurotransmitter release is an underlying step in translating sound. Thus, understanding nature of the synaptic fusion is key to understand the hearing mechanism. Extraordinary large excitatory postsynaptic currents (EPSCs) have been observed in the auditory hair cell synapse, and its origin has been controversial. It is not known yet whether the size and shape of the EPSCs are results of a big vesicle or many small vesicles. We report our numerical simulation of the vesicular fusion process from calcium channel process to the generation of EPSC currents. Our numerical experiments indicate that the origin of the large EPSC with its mysterious form is close to the scenario of the multivesicular release. The large EPSCs might be triggered by strong calcium channeling of the calcium channel clusters.