Muscle-type nicotinic acetylcholine receptor (muscle nAChR)

The muscle-type nicotinic acetylcholine receptor (nAChR) is a pentameric ligand-gated ion channel located at the postsynaptic membrane of neuromuscular junctions. It plays a critical role in mediating synaptic transmission from motor neurons to skeletal muscle fibers, leading to muscle contraction. Upon binding two molecules of acetylcholine, the receptor undergoes conformational changes that open its central cation channel, allowing sodium influx and potassium efflux, generating an endplate potential that triggers muscle action potentials and contraction. Mutations are linked to congenital myasthenic syndromes, and autoantibodies cause myasthenia gravis.

Agonist binding opens the channel, allowing Na+ influx and K+ efflux, leading to depolarization and muscle contraction. Antagonists and inhibitors block the channel or stabilize closed/desensitized states.