Recycling of the Membrane of Synaptic Vesicles

After synaptic vesicles have released neurotransmitter into the synaptic cleft, the following takes place: In "kiss and run," the vesicle fuses with the presynaptic membrane, releases the neurotransmitter, reseals, leaves the docking site, becomes refilled with the neurotransmitter, and mixes with other vesicles in the terminal button. In "merge and recycle," the vesicle completely fuses with the postsynaptic membrane, losing its identity. Extra membrane from fused vesicles pinches off into the cytoplasm and forms vesicles, which are filled with the neurotransmitter. The membranes of vesicles in the reserve pool are recycled through a process of bulk endocytosis. Large pieces of the membrane of the terminal button fold inward, break off, and enter the cytoplasm. New vesicles are formed from small buds that break off of these pieces of membrane.