Both receptors consist of five subunits. The α7 nicotinic acetylcholine receptor (nAChR) consists of five α7 subunits and is called an α7 homo-oligomeric nAChR (top). The α4β2 nAChR is composed of two α4 subunits and three β2 subunits and thus is called an α4β2 heteromeric nAChR (bottom). In both nAChRs, the subunits are arranged around a central pore or channel that opens when agents such as acetylcholine or nicotine bind to the nAChR, allowing positively charged ions to flow through the channel into the cell. The α7 nAChR principally allows passage of calcium (Ca2+) ions, whereas the a4β2 nAChR allows passage of both calcium and sodium (Na+).
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Prepared: December 2008