The fast, initial phase of calcium ion-induced neurotransmitter release, via exocytosis, into the synaptic cleft. This depends on low affinity calcium sensors and typically begins a fraction of a millisecond after Ca2+ influx, and decays rapidly (1-10ms) with a decay constant of around 5-10ms. The underlying molecular mechanisms of this process are distinct from those of the later, slow phase of release.
synchronous, calcium ion-dependent exocytosis of neurotransmitter