Receptors, Opioid, muReceptors, OpioidAnalgesics, OpioidReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesNarcotic AntagonistsNaloxoneOpioid-Related DisordersNaltrexoneEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-MorphineNarcoticsSynthetic BiologyEndorphinsEnkephalin, D-Penicillamine (2,5)-DynorphinsBuprenorphineEnkephalin, LeucineGenes, SyntheticEnkephalin, Leucine-2-AlaninePainDiprenorphinebeta-EndorphinBenzeneacetamidesAnalgesicsMolecular Sequence DataAmino Acid SequenceDrug ToleranceFentanylMorphinansOligopeptidesMethadonePain MeasurementHydromorphonePeptidesDose-Response Relationship, DrugPyrrolidinesBenzomorphansAnalgesiaSubstance Withdrawal SyndromeOpiate Substitution TreatmentHeroinChronic PainPeptide FragmentsPrescription Drug MisuseLevorphanolRats, Sprague-DawleyMorphine DependenceDiterpenes, ClerodaneButorphanolPrescription DrugsHeroin DependenceStereoisomerismLigandsKineticsOxymorphoneBase SequenceEthylketocyclazocineBenzylidene CompoundsMorphine DerivativesInjections, SpinalMolecular StructurePain, IntractableBinding, CompetitiveD-Ala(2),MePhe(4),Met(0)-ol-enkephalinDrug OverdoseAnalgesics, Non-NarcoticPain ThresholdCyclazocineCell LineBinding SitesTime FactorsPeriaqueductal GrayHyperalgesiaAlfentanilDrug InteractionsGuanosine 5'-O-(3-Thiotriphosphate)Radioligand AssayProtein BindingTramadolNalbuphineHydrocodonePiperidinesVaccines, SyntheticBrainSpiro CompoundsProtein PrecursorsSufentanilSubstrate SpecificityGuinea PigsLoperamideCells, CulturedSomatostatinCricetinaeCHO CellsRecombinant ProteinsOpiate AlkaloidsRNA, Messenger