Injections, SpinalMorphineInfusion Pumps, ImplantableSpinal CordAnalgesics, OpioidMuscle Relaxants, CentralAnalgesicsAnesthesia, SpinalHyperalgesiaPain MeasurementBupivacaineAnalgesia, ObstetricalPainInfusions, SpinalSufentanilClonidineBaclofenSpinal NervesPain, IntractableAnalgesiaRats, Sprague-DawleyAnesthetics, LocalNeostigmineSubarachnoid SpaceMuscle SpasticityFentanylPain ThresholdNeuralgiaAnesthesia, ObstetricalPruritusMeningesMeningitisDose-Response Relationship, DrugMeningeal NeoplasmsPain, PostoperativeAdjuvants, AnesthesiaNociceptorsCyclohexanecarboxylic AcidsCerebrospinal FluidNaloxoneDrug ToleranceMethotrexateCesarean SectionOligoclonal BandsAnalgesics, Non-NarcoticPosterior Horn CellsBehavior, AnimalCisterna MagnaAdrenergic alpha-AgonistsNarcotic AntagonistsLidocaineFormaldehydeLeukemic InfiltrationPhysical StimulationHyperesthesiaSciatic NeuropathyPeripheral Nerve InjuriesAnalgesia, EpiduralAminesMeningeal CarcinomatosisTetanus AntitoxinPeripheral Nervous System DiseasesAnesthesia, EpiduralNociceptive PainVisceral PainInfusion PumpsDouble-Blind MethodNociceptionPrecursor Cell Lymphoblastic Leukemia-LymphomaCerebrospinal Fluid RhinorrheaInjections, EpiduralAmitriptylineCarrageenanLyme NeuroborreliosisCytarabineCentral Nervous System NeoplasmsSpinal Nerve RootsMeperidineLigationomega-ConotoxinsReflexReceptors, OpioidSpinal PunctureCentral Nervous System DiseasesSubstance PKetorolacHot TemperatureInjections, IntraventricularReceptors, Opioid, muDexmedetomidineUrinary Bladder CalculiCranial IrradiationAdrenergic alpha-2 Receptor AgonistsDizocilpine MaleateLabor, ObstetricHeroinReceptors, N-Methyl-D-AspartateAntipruriticsDynorphinsSpinal Cord Injuries