The alpha-4 beta-2 nicotinic receptor, also known as the ñ4ò2 receptor, is a type of nicotinic acetylcholine receptor implicated in learning, consisting of ñ4 and ò2 subunits. It is located in the brain, where activation yields post- and presynaptic excitation, mainly by increased Na<sup>+</sup> and K<sup>+</sup> permeability.
Stimulation of this receptor subtype is also associated with growth hormone secretion. People with the inactive CHRNA4 mutation Ser248Phe are an average of 10 cm (4 inches) shorter than average and predisposed to obesity. A 2015 review noted that stimulation of the ñ4ò2 nicotinic receptor in the brain is responsible for certain improvements in attentional performance; among the nicotinic receptor subtypes, nicotine has the highest binding affinity at the ñ4ò2 receptor (k<sub>i</sub>=1 ), which is also the primary biological target that mediates nicotine's addictive properties.
The receptors exist in the two stoichiometries:
The ñ4ò2 receptor assemble in two distinct stoichiometric forms. One stoichiometry contains three ñ4 and two ò2 subunits [ (ñ4)<sub>3</sub>(ò2)<sub>2</sub> ] whereas the other stoichiometry contains two ñ4 and three ò2 [ (ñ4)<sub>2</sub>(ò2)<sub>3</sub> ]. The x-ray structure of the (ñ4)<sub>2</sub>(ò2)<sub>3</sub> receptor is known since 2016 and reveals a circular ñâÂÂòâÂÂòâÂÂñâÂÂò ordering of subunits.
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