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 DiseaseAnalgesiaGene FrequencyPain MeasurementGenetic TestingRewardReceptors, OpioidInjections, SpinalDose-Response Relationship, DrugStreet DrugsHaplotypesPainNucleus AccumbensBehavior, AnimalSubstance Abuse Treatment CentersAnalgesicsPain, PostoperativeOpiumRats, Sprague-DawleyPolymorphism, Single NucleotideConditioning, OperantGenotypeTobacco Use DisorderHydromorphoneDopamineDopamine Uptake InhibitorsCompulsive BehaviorSubstance Abuse DetectionNalorphineOxycodoneDrug-Seeking BehaviorEnkephalinsReceptors, Opioid, deltaReinforcement (Psychology)Enkephalin, Ala(2)-MePhe(4)-Gly(5)-AlcoholismOpiate Substitution TreatmentAnalgesia, Patient-ControlledDrug OverdoseBrainNicotineReceptors, Opioid, kappaFentanylMethamphetamineVentral Tegmental AreaPeriaqueductal GrayLimbic SystemMotivationConditioning (Psychology)MorphinansDrug InteractionsCentral Nervous System StimulantsTime FactorsMotor ActivityMeperidinePentazocineImpulsive BehaviorAmphetamine-Related DisordersExtinction, PsychologicalDrug and Narcotic ControlNalbuphineThebaineCuesSubstance Abuse, IntravenousPain ThresholdInjections, IntravenousDrug UsersReinforcement ScheduleEndorphinsGas Chromatography-Mass SpectrometryGamblingAnalysis of VarianceOxymorphoneOpioid PeptidesAnalgesia, EpiduralDouble-Blind Method