Although CHRNA6 and CHRNB3 are adjacent to each other it is biologically plausible that the α6 and β3 subunits may affect slightly different components of nicotine addiction. The β3 subunit is found in receptors lacking α6, and has no acetylcholine binding site. nAChR receptors with β3 localize with α3 and β4 in the interpeduncular nucleus and medial habenula, whereas receptors with β3, α6 and β2 are found in the substantia negra, VTA, striatum, and locus coeruleus (Gotti et al, 2006). Likewise, α6β2 containing receptors (lacking β3) are found in the superior colliculus and have been shown to be involved in GABA release (Gotti et al, 2006). Analysis of quit attempts suggests that this measure may have a strong underlying genetic component that can be explained in part by the CHRNA6 and CHRNB3 genes (Table 6).
