NicotineReceptors, NicotinicNicotinic AgonistsTobacco Use DisorderGanglionic StimulantsMecamylamineCotinineNicotinic AntagonistsChewing GumSubstance Withdrawal SyndromeTobacco Use Cessation ProductsSmoking CessationSmokingAdministration, CutaneousDihydro-beta-ErythroidineTarsSelf Administrationalpha7 Nicotinic Acetylcholine Receptor