Nicotinic acetylcholine receptors

The Nicotinic receptors (nAChR) are subdivided into muscle types and neuronal types. The muscle types are bringing together from α1, β1, δ, γ or ? subunits in a 2:1:1:1 stoichiometry, whereas the neuronal types are a variety of combinations of 12 subunits, α2–α10 and β2–β4 as shown in figure.

Each of the α-subunits has the binding site for acetylcholine; therefore each receptor binds two molecules of ACh. The binding of one molecule of ACh to a receptor makes binding of the second simpler. This is an illustration of allostery. Most of the nAChR channels are nonselective cation conductances permitting Na+ influx and K+ efflux, via some configurations, for illustration the homomeric (α7)5, are calcium conductances. The total current is inward (that is depolarizing) therefore ACh is excitatory at the nicotinic receptors.