A MECHANISM FOR DISCHARGE OF CHARGED EXCITATORY NEUROTRANSMITTER

Excitatory neurotransmitter is charged, so that emptying of a transmit ter-containing vesicle (discharge) would seem to require considerable energy. Even if the energy problem is surmounted and discharge thereby made possible, there is still a problem of making the discharge fast enough (considerably less than 1 ms). Proposed here is a mechanism whe rein discharge of charged transmitter is accompanied by the influx of cocharged ions or coefflux of counter-charged particles (ion interchan ge). It is shown theoretically that ion interchange obviates the neces sity for a separate energy source and can provide the observed rapid V esicle discharge.