DIFFUSION CANNOT GOVERN THE DISCHARGE OF NEUROTRANSMITTER IN FAST SYNAPSES

In the present work we show that diffusion cannot provide the observed fast discharge of neurotransmitter from a synaptic vesicle during neu rotransmitter release, mainly because it is not sufficiently rapid nor is it sufficiently temperature-dependent. Modeling the discharge from the vesicle into the cleft as a continuous point source, we have dete rmined that discharge should occur in 50-75 mu s, to provide the obser ved high concentrations of transmitter at the critical zone.