ABSTRACT
Most neurotransmitter release occurs by transmitter-loaded synaptic vesicles fusing with the presynaptic membrane and discharging their contents into the synaptic cleft. This is exocytosis. It is triggered by the arrival at the nerve terminal of an action potential which causes a transient and highly localized influx of Ca2+. After release the vesicle membrane is recycled from the presynaptic membrane to form new vesicles by endocytosis. The vesicles are subsequently loaded with transmitter via active transporters localized in the vesicle membrane.
