Table 2.

Likely combinations of α and β subunits that produce functional neuronal nAChR subtypes in the central nervous system. Evidence for the existence of particular subunit combinations is summarized from electrophysiological and immunoprecipitation data obtained from oocyte and mammalian cell line expression systems.

α Subunit	Combines with β subunits	Reference
α2	β2 or β4	(Duvoisin et al., 1989; Papke et al., 1989)
α3	β2 or β4; β3 and 4	(Duvoisin et al., 1989; Papke et al., 1989; Groot-Kormelink et al., 1998)
α4	β2 or β4; β2 and β3 and β4	(Duvoisin et al., 1989; Papke et al., 1989)
α6	β2 or β4; β3 and β4	(Gerzanich et al., 1997; Fucile et al., 1998; Kuryatov et al., 2000)
α7	None (pentamer)	(Couturier et al., 1990)
α2 and α5	β2	(Balestra et al., 2000)
α3 and α5	β2 or β4; β2and β4	(Conroy and Berg, 1995; Wang et al., 1996)
α3 and α6	β2 or β4; β3 and β4	(Vailati et al., 1999; Kuryatov et al., 2000)
α4 and α5	β2	(Ramirez-Latorre et al., 1996)
α6 and α5	β2	(Kuryatov et al., 2000)
α4 and α6 and α5	β2	(Klink et al., 2001)