Recruitment of presynaptic vesicles and facilitation of transmitter release

Facilitation, an enhancement of neuronal secretion by repetitive stimulation, is due to an increase in the number of vesicles that fuse with the presynaptic membrane and release neurotransmitter in response to an action potential. We performed Monte-Carlo simulation of calcium-dependent priming and release of synaptic vesicles and simulated facilitation of transmitter release. The model incorporated the pools of docked, primed, and released vesicles and stochastic calcium-dependent transitions between these pools. The model was validated by comparison of the time-course of transmitter release, its variability, and the magnitude of facilitation with electrophysiology measurements of transmitter release at the lobster neuromuscular synapse.