Receptors, Opioid, muReceptors, OpioidAnalgesics, OpioidReceptors, Opioid, deltaLigandsReceptors, Opioid, kappaOpioid PeptidesNarcotic AntagonistsNaloxoneOpioid-Related DisordersNaltrexoneEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-MorphineCD40 LigandNarcoticsEnkephalin, D-Penicillamine (2,5)-EndorphinsDynorphinsFas Ligand ProteinBuprenorphineEnkephalin, LeucineEnkephalin, Leucine-2-AlanineDiprenorphinePainbeta-EndorphinBenzeneacetamidesAnalgesicsProtein BindingMorphinansDrug ToleranceFentanylBinding SitesMethadonePain MeasurementHydromorphoneRANK LigandMolecular Sequence DataDose-Response Relationship, DrugBenzomorphansPyrrolidinesAmino Acid SequenceModels, MolecularSignal TransductionOligopeptidesAnalgesiaSubstance Withdrawal SyndromeBinding, CompetitiveRadioligand AssayOpiate Substitution TreatmentMembrane GlycoproteinsCD30 LigandTNF-Related Apoptosis-Inducing LigandCell LineHeroinKineticsChronic PainRats, Sprague-DawleyCHO CellsLevorphanolStructure-Activity RelationshipPrescription Drug MisuseCells, CulturedMorphine DependenceButorphanolDiterpenes, ClerodaneProtein Structure, TertiaryOX40 LigandPrescription DrugsCricetinaeEthylketocyclazocineProtein ConformationMice, Inbred C57BLHeroin DependenceOxymorphoneMorphine DerivativesInjections, SpinalCyclazocineRecombinant ProteinsMolecular StructureBenzylidene CompoundsCrystallography, X-RayPain, IntractableReceptors, Cell SurfaceTransfectionGuanosine 5'-O-(3-Thiotriphosphate)Pain ThresholdDrug OverdoseAnalgesics, Non-Narcotic4-1BB LigandPeptidesReceptors, sigmaMembrane ProteinsRNA, MessengerTime FactorsPeriaqueductal GrayPentazocinePiperidinesMice, KnockoutHyperalgesia