Acetylcholine

Abstract

Before neurotransmitters had been discovered, the idea that a diffusible molecule could transmit information from one neuron to other, or from a neuron to a muscle cell, seemed a bit far-fetched. However, this viewpoint quickly changed when acetylcholine was definitively identified as a neurotransmitter. Acetylcholine has characteristics that are similar to many neurotransmitters that were subsequently discovered, including that it is synthesized locally in the nerve terminal, it is released from synaptic vesicles, and it acts both as a fast transmitter and as a neuromodulator. Once in the synaptic cleft, it is rapidly degraded by the enzyme acetylcholinesterase. Acetylcholine is used for signaling in both the peripheral and central nervous systems, and it is involved in a wide range of functions, from stimulating muscles to contract to modulating your attention (e.g., the attention you are focusing on while reading this chapter!).