PentazocineNalorphineAnalgesicsAnalgesics, OpioidNarcoticsLevallorphanMeperidineDextropropoxypheneLevorphanolAlphaprodineMorphineMorphinansPapaverCyclazocineIsonipecotic AcidsFentanylMethadoneNaloxonePainDrug and Narcotic ControlAnalgesics, Non-NarcoticBrain ChemistryBrainAnalgesiaNarcotic AntagonistsBrain InjuriesPain MeasurementPain, PostoperativeBrain NeoplasmsBrain MappingCodeineOpiumMagnetic Resonance ImagingOxymorphoneOpioid-Related DisordersLegislation, DrugBrain EdemaDrug ToleranceTramadolOxycodoneAcetaminophenHydrocodoneBrain StemHeroinBrain IschemiaPhenacetinPreanesthetic MedicationPain ManagementTime FactorsHydromorphoneDose-Response Relationship, DrugPain, IntractableRats, Sprague-DawleyReceptors, Opioid, muReceptors, OpioidAnesthetics, LocalBlood-Brain BarrierCerebral CortexSubstance-Related DisordersBupivacaineAnti-Inflammatory Agents, Non-SteroidalButorphanolAlfentanilAnalgesia, Patient-ControlledMorphine DerivativesNeuronsDouble-Blind MethodSpasmPain ThresholdBuprenorphineEndorphinsInert Gas NarcosisSubstance Withdrawal SyndromeMethotrimeprazineNitrous OxideBehavior, AnimalMorphine DependenceBrain AbscessAnesthesiaRats, WistarAlcoholics AnonymousDisease Models, AnimalImage Processing, Computer-AssistedNaltrexoneTreatment OutcomeHypnotics and SedativesHypoxia, BrainHyperalgesiaMitragynaInjections, SpinalDipyroneDrug OverdoseKetonesNerve BlockCerebrovascular CirculationBrain Damage, ChronicBridged CompoundsParamethasoneAnalysis of VarianceBrain Infarction