NicotineNicotinic AgonistsTobacco Use DisorderGanglionic StimulantsReceptors, NicotinicMecamylamineCotinineNicotinic AntagonistsChewing GumSubstance Withdrawal SyndromeTobacco Use Cessation ProductsSmoking CessationSmokingAdministration, CutaneousDihydro-beta-ErythroidineTarsSelf Administrationalpha7 Nicotinic Acetylcholine ReceptorDose-Response Relationship, DrugAzocinesRats, Sprague-DawleyAconitineConditioning, OperantQuinolizinesTobacco, SmokelessTobacco ProductsRewardTobaccoTime FactorsAnabasineBicyclo Compounds, HeterocyclicBehavior, AnimalReinforcement (Psychology)Carbon MonoxideSelf StimulationHexamethoniumDopamineAnalysis of VarianceBenzazepinesBungarotoxinsBrainTobacco Smoke PollutionHexamethonium CompoundsQuinoxalinesNitrosaminesVentral Tegmental AreaMotor ActivitySmokePyridinesNucleus AccumbensRats, Wistar