Muscle-type nicotinic acetylcholine receptor (nAChR) (nAChR)

The muscle-type nicotinic acetylcholine receptor (nAChR) is a pentameric ligand-gated ion channel essential for signaling at the neuromuscular junction (StatPearls: https://www.ncbi.nlm.nih.gov/books/NBK542278/). In adults, it is typically composed of two alpha-1, one beta-1, one delta, and one epsilon subunit, which form a central pore across the postsynaptic membrane (UniProt: https://www.uniprot.org/uniprotkb/P02708/entry). Upon the binding of acetylcholine released from motor neurons, the receptor undergoes a conformational change that allows the influx of sodium and efflux of potassium ions, leading to membrane depolarization and subsequent muscle contraction (PubMed: https://pubmed.ncbi.nlm.nih.gov/30234153/). This receptor is a critical therapeutic target for neuromuscular blocking agents used in clinical anesthesia to induce muscle relaxation and facilitate surgical procedures (NIH: https://www.ncbi.nlm.nih.gov/books/NBK532920/). Dysfunction of the muscle-type nAChR is central to the pathogenesis of myasthenia gravis, where autoimmune antibodies reduce receptor density, and congenital myasthenic syndromes caused by genetic mutations in the receptor subunits (NCBI: https://www.ncbi.nlm.nih.gov/books/NBK1168/).

Other names

Neuromuscular nicotinic acetylcholine receptorMuscle nAChRCholinergic receptor nicotinic muscle-type

Drugs targeting this receptor function as either depolarizing or non-depolarizing neuromuscular blockers. Non-depolarizing agents act as competitive antagonists that bind to the receptor's alpha subunits, preventing acetylcholine from binding and opening the ion channel, which inhibits muscle contraction. Depolarizing agents, such as succinylcholine, act as persistent agonists that cause initial muscle fasciculation followed by a prolonged refractory state where the receptor remains desensitized or the membrane remains depolarized, preventing further action potentials.