MorphineMorphine DependenceMorphine DerivativesAnalgesics, OpioidDrug ToleranceNarcoticsNaloxoneReceptors, Opioid, muNarcotic AntagonistsAnalgesiaInjections, SpinalPain MeasurementProtein BiosynthesisCodeineSubstance Withdrawal SyndromePain, PostoperativeDose-Response Relationship, DrugAnalgesicsStereoisomerismRats, Sprague-DawleyProtein Synthesis InhibitorsRNA, MessengerPainKineticsReceptors, OpioidNaltrexoneMolecular StructureCells, CulturedTime FactorsAnalgesia, Patient-ControlledNalorphineMolecular Sequence DataCycloheximideHeroinEscherichia coliHydromorphoneDNAFentanylEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Periaqueductal GrayMorphinansCell LineDNA ReplicationCyclizationBase SequenceEnkephalinsOxycodonePentazocineTritiumMutationLeucineNalbuphineReceptors, Opioid, deltaLiverTranscription, GeneticCarbon IsotopesMeperidineRNAThebaineDactinomycinPain ThresholdBehavior, AnimalCell-Free SystemOxymorphoneBacterial ProteinsChemistry Techniques, SyntheticRats, Inbred StrainsAnalgesia, EpiduralAmino Acid SequenceDrug InteractionsEndorphinsHot TemperaturePuromycinThymidineChloramphenicolOpiumPeptide BiosynthesisRats, WistarAmino AcidsInjections, SubcutaneousMagnetic Resonance SpectroscopySpinal CordReceptors, Opioid, kappaCell DivisionGene Expression RegulationChemistry, OrganicStructure-Activity RelationshipMethadoneUridineDepression, ChemicalInjections, IntraventricularIndicators and ReagentsDouble-Blind MethodCarbon RadioisotopesCatalysisChromatography, High Pressure LiquidDrug SynergismTemperaturePapaverSignal Transduction