MorphineEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, MethionineEnkephalin, LeucineMorphine DependenceReceptors, Opioid, muAnalgesics, OpioidNarcoticsDrug ToleranceEnkephalin, D-Penicillamine (2,5)-NaloxoneEnkephalin, Leucine-2-AlanineReceptors, OpioidBrainReceptors, Opioid, deltaNarcotic AntagonistsMorphine DerivativesSubstance Withdrawal SyndromeEndorphinsBrain ChemistryRats, Sprague-DawleyNaltrexoneLocus CoeruleusReceptors, Neurokinin-3LevallorphanPeriaqueductal GrayPrionsPrPSc ProteinsDose-Response Relationship, DrugNeurokinin BEthylketocyclazocineOpioid PeptidesCyclazocineTachykininsPain MeasurementAnalgesiaReceptors, TachykininNeuronsEndopeptidase KScrapieReceptors, Opioid, kappaTime FactorsD-Ala(2),MePhe(4),Met(0)-ol-enkephalinPrion DiseasesNucleus AccumbensPainRats, WistarEncephalopathy, Bovine SpongiformSubstance PBehavior, AnimalMice, Inbred C57BLCockatoosBrain InjuriesNeurokinin APrPC ProteinsCreutzfeldt-Jakob SyndromeReceptors, Neurokinin-2Brain NeoplasmsHyperalgesiaDynorphinsSpinal CordAdenylate CyclaseGuinea PigsBlotting, WesternRats, Inbred StrainsMononegavirales InfectionsWasting Disease, ChronicAnalgesicsOpioid-Related DisordersKineticsMice, KnockoutBrain MappingInjections, SpinalCattleCyclic AMPSynaptosomesArrestinsG Protein-Coupled Inwardly-Rectifying Potassium ChannelsDrug Administration ScheduleBenzomorphansRNA, Transfer, GlyRNA, MessengerCyclic AMP-Dependent Protein KinasesMolecular Sequence DataTissue ExtractsAmino Acid Sequencebeta-EndorphinChromatography, High Pressure LiquidCarboxypeptidase HNerve Tissue ProteinsTissue DistributionMotor ActivityPeptide FragmentsCricetinaeCerebral CortexBenzeneacetamidesDeerBlood-Brain BarrierMorphinans