Biophysical model of a single synaptic connection: Transmission properties are determined by the cooperation of pre- and postsynaptic mechanisms

A stochastic model of synaptic transmission has been designed on the basis of electrophysiological experiments. The model includes presynaptic mechanisms of recruitment and calcium related release of vesicles, transmitter dynamics in the cleft and postsynaptic receptor kinetics. Monte Carlo simulations of a single synaptic connection are performed and demonstrate that synapses depress during repetitive presynaptic stimulation due to depletion of presynaptic vesicles as well as receptor desensitization. Only for stimulation frequencies below 40 Hz depression is caused solely presynaptically by depletion of vesicles. It is shown that specific physiological conditions determine the frequency dependence of steady state depression currents and set limits on the range of possibly rate-coded transmission. (C) 2001 Elsevier Science B.V. All rights reserved.