EnkephalinsEnkephalin, MethionineEnkephalin, LeucineEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, Leucine-2-AlanineEnkephalin, D-Penicillamine (2,5)-EndorphinsReceptors, OpioidReceptors, Opioid, deltaReceptors, Opioid, muNaloxoneDynorphinsEthylketocyclazocineCyclazocineNarcotic AntagonistsMorphineCarboxypeptidase HBenzomorphansNaltrexoneD-Ala(2),MePhe(4),Met(0)-ol-enkephalinbeta-EndorphinAnalgesics, OpioidReceptors, Opioid, kappaOpioid PeptidesDiprenorphineNarcoticsEtorphineThiorphanOligopeptidesAnalgesicsProtein PrecursorsMorphinansTioproninNeprilysinAdrenal MedullaPyrrolidinesChromaffin GranulesGlobus PallidusBrainSomatostatinIleumDrug ToleranceDihydromorphineVas DeferensGuinea PigsRats, Inbred StrainsSubstance PInjections, IntraventricularCorpus StriatumBenzylidene CompoundsInjections, SpinalCarboxypeptidasesRats, Sprague-DawleyMyenteric PlexusLocus CoeruleusMorphine DerivativesNeurotransmitter AgentsNeuronsBinding, CompetitiveNeuroblastomaDose-Response Relationship, DrugProtease InhibitorsChromaffin SystemNociceptive PainSpinal CordGalaninSubstantia GelatinosaElectric Stimulation