pentameric ligand-gated ion channels, consisting of various heteromeric or homomeric combinations of α (α2–α10) and β (β2–β4) subunits (Albuquerque et al., 2009; Gotti et al., 2009). Most neuronal nAChRs are heteromeric receptors with just two binding sites, but some subunits, such as the α7, form functional homomeric receptors with five binding sites (Changeux, 2009; Gotti et al., 2009). The most abundant of nAChR subtypes in the brain are the α4β2* (*indicates the possibility of other subunits) followed by the α7; correspondingly, the mRNA of these subtypes are found throughout the entire brain. The vast regional distribution and location of nAChRs are thoroughly reported in the following reviews (Gotti and Clementi, 2004; Gotti et al., 2007).
