Nicotinic Acetylcholine Receptors

Abstract Nicotinic receptors are cation‐permeable ion channels activated by the neurotransmitter acetylcholine. The muscle‐type receptor mediates all fast synaptic excitation on voluntary muscle. We review both the structure and the function of muscle/ Torpedo receptor, and the function of several mutants. Recent developments both in knowledge of structure and in analysis of single‐channel records are beginning to throw light on the role of single amino acid residues in the molecular events (the binding of an agonist and the gating of the channel) that lead to channel opening. In the nervous system, nicotinic channels mediate the majority of fast excitation only in autonomic ganglia, but are also present at presynaptic locations. Issues of receptor classification and subunit composition are particularly relevant for neuronal channels because of the numerous subunit combinations possible and because relatively few selective competitive antagonists are available, a situation that may improve with the characterization of alpha‐conotoxins. Inherited mutations in nicotinic channels give rise to rare congenital forms of human disease (myasthenia for muscle and epilepsy for neuronal receptors).