Acetylkolin

Acetylkolin, also known as acetylcholine, is a neurotransmitter used by neurons in both the peripheral and central nervous systems. It is a positively charged ester formed from choline and acetate and serves as the primary transmitter at the vertebrate neuromuscular junction and at many cholinergic synapses in the autonomic nervous system. In neurons, acetylkolin is synthesized from choline and acetyl-CoA by the enzyme choline acetyltransferase (ChAT), stored in synaptic vesicles by the vesicular acetylcholine transporter (VAChT), and released into the synaptic cleft in response to calcium influx during an action potential.

Following release, acetylkolin interacts with cholinergic receptors, including nicotinic receptors at the neuromuscular junction and both nicotinic and muscarinic receptors in various autonomic and central targets. It is rapidly inactivated by the enzyme acetylcholinesterase, which hydrolyzes it to choline and acetate. The choline is reclaimed by the presynaptic terminal through a high-affinity choline transporter for reuse in acetylkolin synthesis.

Physiological roles of acetylkolin span muscle contraction, glandular secretion, and autonomic reflexes in the peripheral nervous system, as well as modulation of attention, learning, memory, arousal, and other cognitive processes in the central nervous system.

Clinical relevance includes involvement in myasthenia gravis and Alzheimer’s disease, where cholinergic transmission is impaired. Treatments often employ acetylcholinesterase inhibitors to elevate synaptic acetylkolin levels. Exposure to organophosphate n toxicants inhibits acetylcholinesterase, causing excessive cholinergic stimulation and potentially life-threatening effects.