Heroin DependenceNarcoticsOpiate AlkaloidsMorphine DerivativesOpioid-Related DisordersMethadoneNaloxoneMorphineCodeineReceptors, OpioidBuprenorphineAnalgesics, OpioidSubstance Abuse DetectionSubstance Withdrawal SyndromeReceptors, Opioid, muNaltrexoneSelf AdministrationDrug OverdoseHeroinEnkephalinsStreet DrugsEndorphinsNarcotic AntagonistsMorphine DependenceEtorphineCocaine-Related DisordersSubstance Abuse, IntravenousOpiumBehavior, AddictiveDihydromorphineEnkephalin, Leucine-2-AlanineSubstance-Related DisordersCyclazocineGas Chromatography-Mass SpectrometryCocaineEnkephalin, LeucineEnkephalin, MethionineEthylketocyclazocineDrug and Narcotic ControlMethadyl AcetateNucleus AccumbensReceptors, Opioid, deltaConditioning, OperantOpiate Substitution TreatmentEnkephalin, Ala(2)-MePhe(4)-Gly(5)-DiprenorphineHydromorphoneDrug ToleranceCrimeDose-Response Relationship, DrugReceptors, Opioid, kappaMorphinansBehavior, AnimalBenzomorphansSubstance Abuse Treatment CentersDrug UsersReinforcement (Psychology)AnalgesiaOxymorphoneNeonatal Abstinence SyndromeForensic MedicineOxycodoneLocus CoeruleusPhenazocineSweatHydrocodoneEuphoriaRewardAnalgesicsFentanylbeta-EndorphinBrainDynorphinsLevallorphanRats, Sprague-DawleyExtinction, PsychologicalPentazocineNalorphineEnzyme Multiplied Immunoassay TechniqueDrug InteractionsFlupenthixolLaw EnforcementReinforcement SchedulePrisonersEnkephalin, D-Penicillamine (2,5)-Conditioning (Psychology)HairTime FactorsPupilPapaverRats, Long-EvansPainImmunoassayLimbic SystemOpioid PeptidesDrug ContaminationNeedle SharingAmphetamine-Related DisordersAdministration, SublingualClonidine