Heroin DependenceMethadoneMorphineMorphine DerivativesNarcoticsHeroinMorphine DependenceBuprenorphineAnalgesics, OpioidReceptors, Opioid, muBehavior, AddictiveOpioid-Related DisordersOpiate Substitution TreatmentNuclear Receptor Subfamily 4, Group A, Member 2NaloxoneDrug ToleranceSubstance-Related DisordersSubstance Withdrawal SyndromeNarcotic AntagonistsCryptochromesCodeineCocaineMethadyl AcetateLinkage DisequilibriumSelf AdministrationNaltrexoneStreet DrugsDose-Response Relationship, DrugSubstance Abuse DetectionAnalgesiaOpiumPain MeasurementGenetic Predisposition to DiseaseGene FrequencyNeonatal Abstinence SyndromeReceptors, OpioidPainRewardInjections, SpinalGenetic TestingDrug OverdoseAnalgesicsHaplotypesBehavior, AnimalHydromorphonePain, PostoperativeRats, Sprague-DawleyNucleus AccumbensSubstance Abuse Treatment CentersPolymorphism, Single NucleotideConditioning, OperantOxycodoneGenotypeNalorphineTobacco Use DisorderSubstance Abuse, IntravenousDopamine Uptake InhibitorsDrug InteractionsReceptors, Opioid, deltaDopamineReinforcement (Psychology)EnkephalinsCompulsive BehaviorDrug-Seeking BehaviorFentanylCocaine-Related DisordersEnkephalin, Ala(2)-MePhe(4)-Gly(5)-BrainTime FactorsDrug and Narcotic ControlAlcoholismPyrrolidinesNicotineAnalgesia, Patient-ControlledMeperidineMotivationMethamphetamineGas Chromatography-Mass SpectrometryPentazocineReceptors, Opioid, kappaDrug UsersStereoisomerismCentral Nervous System StimulantsVentral Tegmental AreaPeriaqueductal GrayLimbic SystemMotor ActivityPain, IntractableConditioning (Psychology)MorphinansCrimeImpulsive BehaviorAmphetamine-Related DisordersTramadolExtinction, PsychologicalAnalysis of VarianceNalbuphineInjections, IntravenousReinforcement ScheduleDouble-Blind Method