Hundredth Anniversary of the “Synapse”: II. Study of the Cholinergic Synapse

Major contributions to the research on the cholinergic synapse in the last five decades was described. The original notion of active zone, composed of a presynaptic dense projection and associated synaptic vesicles, was analyzed in order to underline its functional meaning in synaptic transmission. An overview was done on the findings made on acetylcholine release (ultrastructural aspect, cytochemistry, non-vesicular hypothesis and mediatophore), acetylcholinesterase (ultrastructural localization, discovery of molecular polymorphism) and acetylcholine receptor (characterization, purification). The structural base of the smallest functional unit in a synapse was attributed to a single synaptic vesicle of active zone and corresponding area of synaptic cleft and postsynaptic membrane interacting with the neurotransmitter released from the vesicle.