Acetylcholine (ACh) is a neurotransmitter, which means it is a chemical messenger that transmits signals between nerve cells and between nerves and muscles. It plays a crucial role in the functioning of the nervous system, particularly in the parts of the nervous system that control voluntary and involuntary movements.
In the peripheral nervous system, ACh is released by neurons that innervate skeletal muscles, where it binds to receptors on the muscle cells, causing them to contract. This process is essential for movement and muscle control.
In the central nervous system, ACh is involved in a range of functions, including attention, learning, memory, and regulating the sleep-wake cycle. It is particularly important in the hippocampus, a region of the brain that is critical for learning and memory.
ACh is synthesized in nerve terminals from choline and acetyl coenzyme A (AcCoA) by the enzyme choline acetyltransferase (ChAT). It is then stored in vesicles until it is released in response to an action potential.
The activity of ACh is terminated by the enzyme acetylcholinesterase (AChE), which breaks down ACh into choline and acetate. Choline is then taken back up into the nerve terminal, where it is used to synthesize new ACh.
Abnormalities in ACh signaling have been implicated in a range of neurological and psychiatric disorders, including Alzheimer’s disease, Parkinson’s disease, and schizophrenia. Drugs that target ACh signaling, such as acetylcholinesterase inhibitors, are used in the treatment of some of these conditions.