Nicotine is a naturally occurring alkaloid in tobacco. Nicotine is highly addictive (Davis, 1988), and the nicotinic acetylcholine receptors, in part, mediate the effects of nicotine in the body (Lindstrom, 2003; Tapper et al., 2004). These receptors are pentameric molecular assemblies of nicotinic acetylcholine receptor (nAChR) subunits, which are coded by a family of distinct cholinergic nicotinic receptor (CHRN) genes. These subunits, and the receptors assembled from them, fall into two classes, neuronal and neuromuscular. In humans the neuronal subunits consist of α2 through α7, α9, α10, and β2 through β4; the muscle nAChRs are α1, β1, δ, ε and γ. The α8 subunit has been detected in avian tissue but not in mammals.
