AnalgesicsAnalgesics, OpioidAnalgesics, Non-NarcoticAnalgesiaPainPain MeasurementMorphinePain, PostoperativeTramadolPhenacetinAcetaminophenDextropropoxypheneAnti-Inflammatory Agents, Non-SteroidalDrug ToleranceCodeinePain ThresholdMeperidineFentanylPentazocinePain ManagementReceptors, Opioid, muOxycodoneAnesthetics, LocalDipyroneHyperalgesiaInjections, SpinalBupivacaineAnalgesia, EpiduralNaloxoneDouble-Blind MethodAnalgesia, Patient-ControlledCarrageenanKetoprofenKidney Papillary NecrosisTolmetinNefopamReceptors, OpioidHydrocodoneNarcotic AntagonistsKetorolacPain, IntractableIbuprofenNociceptionNeuralgiaHydromorphoneDose-Response Relationship, DrugNalorphineAcupuncture AnalgesiaCyclohexanecarboxylic AcidsBuprenorphineEdemaNociceptorsDiclofenacAnalgesia, ObstetricalButorphanolOxymorphoneMorphine DerivativesMorphinansMeptazinolNociceptive PainHypnotics and SedativesNarcoticsAlfentanilAntipyreticsKetamineAcetic AcidNalbuphineAcute PainNerve BlockChronic PainRats, Sprague-DawleyDexmedetomidineCyclazocineKetorolac TromethamineSufentanilLidocaineEndorphinsAnti-Inflammatory AgentsPiroxicamAminesNitrous OxideClonidineNonprescription DrugsNaltrexoneAmidesReceptors, Opioid, deltaLevorphanolOpioid PeptidesElectroacupunctureOpioid-Related DisordersPrilocainePostoperative Nausea and VomitingPlant ExtractsSpinal CordAspirinAnesthesia, SpinalAnesthetics, DissociativeFormaldehydeTromethamineBehavior, Animal