Steps in neuronal exocytosis.

Synaptic vesicles containing neurotransmitters dock with the plasma membrane. The docked vesicles are primed for secretion in an ATP/Mg⁺⁺-dependent process that readies them for immediate release in response to local increases in Ca⁺⁺ secondary to membrane depolarization. Subsequently the vesicle and plasma membranes fuse (through a SNARE-dependent mechanism) and the vesicle contents are released into the extracellular space.