nicotinic receptor (nicotinic acetylcholine receptor, nAChR)

^[1]^[2]^[3]^[4]^[5]

Function

ionotropic nicotinic receptors mediate postsynaptic excitatory responses at the neuromuscular junction
nicotinic receptors may also act presynaptically to modulate acetylcholine release in the periphery
simultaneous binding of 2 molecules of acetylcholine is required for opening of the ion channel
a conformational change that affects all subunits results in opening of the ion channel, permeable primarily to Na+ & secondarily Ca+2
within the brain, nicotinic receptors function as ligand-gated ion channels linked to rapidly desensitizing Ca2+ influx, with variable permeability of Na+ relative to Ca+2
role in modulation of release of several neurotransmitters (glutamate, GABA & dopamine), mediating &/or modulating synaptic transmission & plasticity^[4]
nicotinic receptors are inhibited by neuromuscular blocking agents.

skeletal muscle receptors consist of pentamers of (alpha)2-beta-gamma-delta
in mature muscle endplates, the gamma subunit is replaced by an epsilon subunit, (alpha)2-beta-delta-epsilon
in the mammalian CNS, nine different alpha subunits (2-10) & three different beta subunits (2-4) have been described
it is assumed that most receptors are heteropentameric structures, with various combinations of alpha & beta subunits, but some receptors may form as homopentamers, notably alpha-7 (CHRNA7)
these alpha-7 homopentamers along with those containing alpha-4 & beta-2 subunits are the most abundant in brain.

↑ Armstrong TINS 12(3) 117 1989
↑ Kullberg et al Proc Natl Acad Sci U S A 1990 Mar;87(6):2067-71
↑ Barnard EA. Receptor classes and the transmitter-gated ion channels. Trends Biochem Sci. 1992 Oct;17(10):368-74. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/1360717
↑ ^4.0 ^4.1 ^4.2 Fabian-Fine R, Skehel P, Errington ML, Davies HA, Sher E, Stewart MG, Fine A. Ultrastructural distribution of the alpha7 nicotinic acetylcholine receptor subunit in rat hippocampus. J Neurosci. 2001 Oct 15;21(20):7993-8003. PMID: https://www.ncbi.nlm.nih.gov/pubmed/11588172
↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996 pg 178