EnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, LeucineEnkephalin, MethionineReceptors, Opioid, muReceptors, OpioidEnkephalin, D-Penicillamine (2,5)-Enkephalin, Leucine-2-AlanineReceptors, Opioid, deltaAnalgesics, OpioidEndorphinsReceptors, Opioid, kappaNaloxoneOpioid PeptidesReceptors, Neurokinin-3Narcotic AntagonistsEthylketocyclazocineMorphineNeurokinin BCyclazocineTachykininsReceptors, TachykininD-Ala(2),MePhe(4),Met(0)-ol-enkephalinNaltrexoneDynorphinsSubstance PNarcoticsNeurokinin AReceptors, Neurokinin-2Benzeneacetamidesbeta-EndorphinDiprenorphineBenzomorphansOpioid-Related DisordersRNA, Transfer, GlyAnalgesicsCarboxypeptidase HMorphinansGuinea PigsOligopeptidesDrug TolerancePyrrolidinesDose-Response Relationship, DrugNeurokinin-1 Receptor AntagonistsPainBuprenorphineProtein PrecursorsGlycineAmino Acid SequencePain MeasurementFentanylThiorphanReceptors, Neurokinin-1EtorphinePiperidinesMolecular Sequence DataRats, Sprague-DawleyInjections, SpinalPeptide FragmentsAnalgesiaBrainSomatostatinBenzylidene CompoundsNeprilysinMorphine DerivativesMethadoneSubstance Withdrawal SyndromeAdrenal MedullaIleumKineticsTioproninDihydromorphineMorphine DependenceVas DeferensAlanineIrisBinding, CompetitiveStructure-Activity RelationshipInjections, IntraventricularRadioligand AssayGlobus PallidusSpinal CordGuanosine 5'-O-(3-Thiotriphosphate)Periaqueductal GrayChromaffin GranulesHydromorphoneBenzamidesRats, Inbred StrainsLocus CoeruleusMutagenesis, Site-DirectedPeptidesAminolevulinic AcidNeuronsOxymorphoneAmino Acid SubstitutionModels, MolecularCorpus StriatumMyenteric PlexusCarboxypeptidasesNeurotransmitter Agents