Distinct contributions of nicotinic acetylcholine receptor subunit alpha4 and subunit alpha6 to the reinforcing effects of nicotine. by Exley, R, Maubourguet, N, David, V, Eddine, R, Evrard, A, Pons, S, Marti, F, Threlfell, S, Cazala, P, McIntosh, J, Changeux, J, Maskos, U, Cragg, S, Faure, P