Spinal CordSpinal Cord InjuriesReceptors, Opioid, muReceptors, OpioidAnalgesics, OpioidReceptors, Opioid, deltaSpinal Cord DiseasesReceptors, Opioid, kappaSpinal Cord CompressionSpinal Cord NeoplasmsOpioid PeptidesSpinal Cord IschemiaInjections, SpinalParaplegiaNarcotic AntagonistsSpinal Nerve RootsSpinal NervesNaloxoneMotor NeuronsSpinal Cord RegenerationPainSpinal CanalAnesthesia, SpinalRats, Sprague-DawleySpinal NeoplasmsCervical VertebraeMorphineQuadriplegiaNaltrexoneOpioid-Related DisordersThoracic VertebraeSpinal DiseasesPosterior Horn CellsEnkephalinsUmbilical CordEnkephalin, Ala(2)-MePhe(4)-Gly(5)-LaminectomyLumbosacral RegionGanglia, SpinalRecovery of FunctionDynorphinsNerve RegenerationSpinal StenosisAxonsPain MeasurementLocomotionSpinal Cord StimulationSpinal FusionNarcoticsSpinal InjuriesHyperalgesiaEnkephalin, D-Penicillamine (2,5)-AnalgesicsAnterior Horn CellsMyelitisNeuronsEndorphinsCordotomyParalysisNeuralgiaMuscular Atrophy, SpinalDisease Models, AnimalEnkephalin, LeucineNociceptorsElectric Stimulation TherapyElectric StimulationTime FactorsBuprenorphineMyelographyNeurons, AfferentMotor ActivityAfferent PathwaysDrug ToleranceSpineEpidural SpaceHindlimbReflexUrinary Bladder, NeurogenicLumbar VertebraePain ThresholdHematoma, Epidural, SpinalEnkephalin, Leucine-2-AlanineAnalgesiaCentral Nervous SystemLampreysbeta-EndorphinPhysical StimulationFentanylInterneuronsAutonomic DysreflexiaCatsMagnetic Resonance ImagingElectromyographyDose-Response Relationship, DrugImmunohistochemistryPyramidal TractsTuberculosis, SpinalMyelin SheathNeurogliaDiprenorphine