Opiate AlkaloidsNarcoticsOpioid-Related DisordersReceptors, OpioidNaloxoneMorphineCodeineHeroinEndorphinsSynthetic BiologyNarcotic AntagonistsEnkephalinsMethadoneAnalgesics, OpioidMorphine DerivativesGenes, SyntheticEtorphineHeroin DependenceOpiumSubstance Abuse DetectionReceptors, Opioid, muSubstance Withdrawal SyndromeEnkephalin, Leucine-2-AlanineDihydromorphineCyclazocineMorphine DependenceBuprenorphineNaltrexoneEnkephalin, MethionineEnkephalin, LeucineEthylketocyclazocineMolecular Sequence DataAmino Acid SequenceDiprenorphineMethadyl AcetatePeptidesGas Chromatography-Mass SpectrometryMorphinansEnkephalin, Ala(2)-MePhe(4)-Gly(5)-BenzomorphansStreet DrugsOxymorphoneDrug ToleranceOligopeptidesOxycodoneLocus CoeruleusReceptors, Opioid, deltaPhenazocineAnalgesiabeta-EndorphinHydrocodoneHydromorphoneDynorphinsLevallorphanPeptide FragmentsKineticsAnalgesicsDose-Response Relationship, DrugPentazocineDrug OverdoseReceptors, Opioid, kappaNalorphineBase SequenceFentanylEnzyme Multiplied Immunoassay TechniqueBrainNeonatal Abstinence SyndromeSubstance-Related DisordersBinding, CompetitiveStereoisomerismOpioid PeptidesRats, Sprague-DawleyCannabinoidsMolecular StructureTime FactorsPainBinding SitesEthylmorphineVaccines, SyntheticCell LineChromatography, High Pressure LiquidDesigner DrugsRats, Inbred StrainsEnkephalin, D-Penicillamine (2,5)-EpitopesForensic MedicineNucleus AccumbensSubstrate SpecificityBehavior, AnimalReceptors, PhencyclidineChemistry Techniques, SyntheticLigandsClonidineCocaineEscherichia coliProtein BindingEuphoriaCells, CulturedLoperamideRecombinant Proteins