Figure 4.
Stochastic model of neurotransmitter release. A, Diagrammatic view of deterministic (left) and stochastic (right) models of release. The deterministic model tracked the average behavior of a synapse, using fixed rates of release and recovery of a pool of vesicles, as well as desensitization and recovery of postsynaptic receptors (see Materials and Methods). The stochastic model tracked multiple sites, each with its own pool of vesicles and receptors. Release and recovery were governed by binomially distributed random processes. The deterministic model used seven parameters, and two parameters were added for the stochastic model. B, Activity of a single release site, showing fluctuations in vesicle pool size (NV) and extracellular glutamate concentration during a train of activity. C, The stochastic model captured both mean and variance of synaptic transmission. Symbols show mean (top) and SD (bottom) of voltage-clamp data from the cell depicted in Figure 2A–C. Solid lines show mean and SD of conductances given by the stochastic model.