Receptors, Opioid, muReceptors, Opioid, kappaReceptors, OpioidAnalgesics, OpioidReceptors, Opioid, deltaOpioid PeptidesNarcotic AntagonistsNaloxoneNaltrexoneOpioid-Related DisordersImmunoglobulin kappa-ChainsEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-DynorphinsNarcoticsMorphineEnkephalin, D-Penicillamine (2,5)-EndorphinsBenzeneacetamidesBuprenorphineEnkephalin, LeucineEnkephalin, Leucine-2-AlanineDiprenorphinePainPyrrolidinesAnalgesicsbeta-EndorphinBenzomorphansDrug ToleranceFentanylPain MeasurementMorphinansMethadoneHydromorphoneEthylketocyclazocineImmunoglobulin Light ChainsNF-kappa BDiterpenes, ClerodaneAnalgesiaGene Rearrangement, B-Lymphocyte, Light ChainSubstance Withdrawal SyndromeImmunoglobulin lambda-ChainsOpiate Substitution TreatmentI-kappa B ProteinsButorphanolDose-Response Relationship, DrugLevorphanolHeroinCyclazocineChronic PainPrescription Drug MisuseReproducibility of ResultsMorphine DependenceRats, Sprague-DawleyPrescription DrugsImmunoglobulin Variable RegionMolecular Sequence DataHeroin DependenceMorphine DerivativesOligopeptidesInjections, SpinalAnalgesics, Non-NarcoticOxymorphoneBase SequencePain, IntractableGenes, ImmunoglobulinPain ThresholdNalbuphineDrug OverdoseBenzylidene CompoundsCell LineHyperalgesiaGuanosine 5'-O-(3-Thiotriphosphate)Radioligand AssayPeriaqueductal GrayD-Ala(2),MePhe(4),Met(0)-ol-enkephalinTranscription Factor RelBDrug InteractionsProto-Oncogene Proteins c-relAlfentanilHydrocodoneTramadolAmino Acid SequenceLigandsSufentanilAzocinesSalviaSpinal CordLoperamideNociceptorsPiperidinesOpiate AlkaloidsPentazocineSensitivity and SpecificityPain, PostoperativeTime FactorsImmunoglobulin Joining RegionPain ManagementBinding, CompetitiveBrain