EnkephalinsMorphineEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, LeucineEnkephalin, MethionineEnkephalin, D-Penicillamine (2,5)-Enkephalin, Leucine-2-AlanineReceptors, Opioid, muEndorphinsReceptors, OpioidMorphine DependenceMorphine DerivativesNaloxoneAnalgesics, OpioidReceptors, Opioid, deltaReceptors, Neurokinin-3EndocytosisNarcotic AntagonistsNeurokinin BEthylketocyclazocineNarcoticsCyclazocineTachykininsDrug ToleranceReceptors, TachykininReceptors, Opioid, kappaD-Ala(2),MePhe(4),Met(0)-ol-enkephalinSubstance PNeurokinin ANaltrexoneReceptors, Neurokinin-2DynorphinsClathrinInjections, SpinalAnalgesicsDose-Response Relationship, DrugOpioid PeptidesArrestinsRNA, Transfer, GlyEtorphineAnalgesiaBenzomorphansPain MeasurementAmino Acid SequenceDynaminsDiprenorphineCell Linebeta-EndorphinMolecular Sequence DataBenzeneacetamidesCarboxypeptidase HGuinea PigsKineticsMorphinansCell MembraneRats, Sprague-DawleyOligopeptidesSubstance Withdrawal SyndromeReceptors, Neurokinin-1Neurokinin-1 Receptor AntagonistsProtein TransportPainCoated Pits, Cell-MembraneEndosomesCodeinePain, PostoperativeCHO CellsCricetinaeGlycinePeriaqueductal GrayFentanylPeptide FragmentsMutagenesis, Site-DirectedCells, CulturedMicroscopy, ConfocalPiperidinesProtein BindingLigandsTransfectionProtein PrecursorsSignal TransductionBrainThiorphanMutationSpinal CordLocus CoeruleusBinding, CompetitiveClathrin-Coated VesiclesNeuronsPeptidesSomatostatinInjections, IntraventricularPhosphorylationPyrrolidinesTime FactorsVirus InternalizationAdaptor Protein Complex 2AlanineIleumStructure-Activity Relationship