AnalgesiaAnalgesicsAnalgesia, EpiduralAnalgesia, ObstetricalAnalgesics, OpioidAnalgesia, Patient-ControlledPain, PostoperativeAnalgesics, Non-NarcoticPain MeasurementMorphinePainBupivacaineAnesthetics, LocalFentanylAcupuncture AnalgesiaTramadolMeperidineInjections, SpinalAnesthesia, EpiduralSufentanilLabor PainNerve BlockPain ThresholdDrug ToleranceDouble-Blind MethodAcetaminophenNaloxoneReceptors, Opioid, muAnesthesia, ObstetricalAmidesPain ManagementLabor, ObstetricAnesthesia, SpinalKetorolacAnti-Inflammatory Agents, Non-SteroidalHydromorphonePhenacetinHyperalgesiaCodeinePentazocinePostoperative Nausea and VomitingReceptors, OpioidOxycodoneNarcotic AntagonistsDextropropoxypheneKetoprofenLidocaineDipyroneKetamineButorphanolCesarean SectionClonidineHypnotics and SedativesAlfentanilConscious SedationAnesthesia, GeneralAnesthesia, CaudalNalbuphinePain, IntractableDose-Response Relationship, DrugInterpleural AnalgesiaMorphine DerivativesNefopamOpioid PeptidesElectroacupunctureNociceptorsLabor Stage, FirstBuprenorphineDexmedetomidineTolmetinNociceptionNitrous OxideAnesthetics, CombinedFemoral NerveNeuralgiaNociceptive PainPregnancyNarcoticsAnesthesia, ConductionProspective StudiesPlacebo EffectPirinitramidePeriaqueductal GrayAdjuvants, AnesthesiaPrilocaineCyclohexanecarboxylic AcidsThoracotomyAnesthetics, DissociativeAnesthesia, LocalAnesthesia and AnalgesiaPain PerceptionRats, Sprague-DawleyMorphinansCarrageenanDiclofenacAmbulatory Surgical ProceduresPostoperative CarePiperidinesOxymorphoneSpinal Cord