Heroin DependenceMorphineMorphine DerivativesMethadoneNarcoticsHeroinMorphine DependenceBuprenorphineReceptors, Opioid, muBehavior, AddictiveAnalgesics, OpioidNuclear Receptor Subfamily 4, Group A, Member 2Drug ToleranceNaloxoneSubstance-Related DisordersSubstance Withdrawal SyndromeOpioid-Related DisordersNarcotic AntagonistsCryptochromesLinkage DisequilibriumCodeineCocaineSelf AdministrationNaltrexoneGenetic Predisposition to DiseaseTobacco Use DisorderGene FrequencyAnalgesiaPain MeasurementDose-Response Relationship, DrugRewardGenetic TestingReceptors, OpioidStreet DrugsInjections, SpinalHaplotypesAlcoholismPainBehavior, AnimalSubstance Abuse Treatment CentersRats, Sprague-DawleyNucleus AccumbensPolymorphism, Single NucleotideAnalgesicsOpiumPain, PostoperativeGenotypeConditioning, OperantDopamineHydromorphoneDopamine Uptake InhibitorsSubstance Abuse DetectionCompulsive BehaviorNalorphineOxycodoneEnkephalinsDrug-Seeking BehaviorOpiate Substitution TreatmentReinforcement (Psychology)Receptors, Opioid, deltaBrainEnkephalin, Ala(2)-MePhe(4)-Gly(5)-NicotineTime FactorsDrug OverdoseAnalgesia, Patient-ControlledMethamphetamineReceptors, Opioid, kappaMotivationAmphetamine-Related DisordersFentanylLimbic SystemVentral Tegmental AreaCentral Nervous System StimulantsImpulsive BehaviorPeriaqueductal GrayDrug InteractionsConditioning (Psychology)MorphinansMotor ActivityPentazocineMeperidineDrug and Narcotic ControlExtinction, PsychologicalNalbuphineCocaine-Related DisordersCuesSubstance Abuse, IntravenousAnalysis of VarianceDrug UsersThebaineInjections, IntravenousPain ThresholdReinforcement ScheduleKineticsGamblingNeuronsEndorphinsGas Chromatography-Mass SpectrometryDouble-Blind Method