EnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, LeucineEnkephalin, MethionineAnalgesiaAnalgesia, EpiduralEnkephalin, D-Penicillamine (2,5)-Enkephalin, Leucine-2-AlanineAnalgesia, ObstetricalEndorphinsReceptors, Opioid, muReceptors, OpioidAnalgesia, Patient-ControlledAnalgesics, OpioidMorphineReceptors, Opioid, deltaReceptors, Neurokinin-3NaloxoneNeurokinin BEthylketocyclazocinePain, PostoperativeCyclazocineTachykininsReceptors, TachykininPain MeasurementNarcotic AntagonistsAnalgesicsD-Ala(2),MePhe(4),Met(0)-ol-enkephalinReceptors, Opioid, kappaBupivacaineSubstance PFentanylAnesthetics, LocalNeurokinin AAcupuncture AnalgesiaReceptors, Neurokinin-2DynorphinsInjections, SpinalPainOpioid PeptidesSufentanilAnesthesia, EpiduralRNA, Transfer, GlyNaltrexoneMeperidinebeta-EndorphinLabor PainBenzeneacetamidesBenzomorphansNarcoticsCarboxypeptidase HNerve BlockDrug ToleranceLabor, ObstetricDose-Response Relationship, DrugGuinea PigsAnesthesia, ObstetricalPiperidinesAmidesDiprenorphineNeurokinin-1 Receptor AntagonistsAnalgesics, Non-NarcoticEtorphineAnesthesia, SpinalPain ThresholdMorphinansTramadolOligopeptidesDouble-Blind MethodGlycineReceptors, Neurokinin-1Morphine DerivativesAmino Acid SequenceThiorphanProtein PrecursorsCesarean SectionPostoperative Nausea and VomitingInterpleural AnalgesiaDihydromorphineRats, Sprague-DawleyMolecular Sequence DataPeriaqueductal GrayNeprilysinPyrrolidinesSpinal CordNociceptive PainPeptide FragmentsElectroacupunctureBrainTioproninAnesthesia, GeneralConscious SedationKetorolacInjections, IntraventricularLabor Stage, FirstHydromorphoneLidocaineAdrenal MedullaPain ManagementAnesthesia, Caudal