A semiquantitative theory of synaptic vesicle movements.

Under the assumption that vesicles are the anatomic correlate of quantal release, the forces governing the movement of synaptic vesicles inside neurons are analyzed. Semiquantitative calculations are presented to show that a diffuse layer field penetrates a few Debye lengths into the axoplasm. This field binds tightly a monolayer of water to the membrane forming the potential barrier for miniature end-plate potential (mepp) release. The action potential destroys the monolayer and pulls the vesicle to the membrane. The vesicles are brought to the synaptic zone and held there by a Na(+) leak in the synaptic membrane. A stochastic theory of synaptic vesicle release is presented to explain experimental results. The rate of vesicle release is fractionated into a rate of membrane contacts by a vesicle and a rate of vesicle discharge per contact.