ClonidineAdrenergic alpha-AgonistsAdrenergic alpha-2 Receptor AgonistsYohimbinePreanesthetic MedicationGuanidineSympatholyticsReceptors, Adrenergic, alpha-2Adrenergic alpha-AntagonistsTrimethylsilyl CompoundsImidazoline ReceptorsReceptors, Adrenergic, alphaGuanidinesAnalgesicsInjections, SpinalGuanfacineOxymetazolineIdazoxanDose-Response Relationship, DrugAdrenergic alpha-2 Receptor AntagonistsNorepinephrineAdjuvants, AnesthesiaBlood PressurePrazosinHeart RateDouble-Blind MethodMorphinePhentolamineReceptors, AdrenergicAnesthetics, LocalAnalgesia, EpiduralTabletsProtein DenaturationPremedicationNaloxoneDioxanesDrug InteractionsHypnotics and SedativesHemodynamicsMedetomidineAnalgesics, OpioidImidazolesNeostigmineMethoxamineDesipramineRats, Sprague-DawleyEpinephrineGuanabenzInjections, IntravenousLidocainePain, PostoperativeAdministration, OralBupivacaineChemistry, PharmaceuticalSympathetic Nervous SystemDexmedetomidineAntihypertensive AgentsMethyldopaPain MeasurementTiloroneDrug StabilityDosage FormsTime FactorsInjections, EpiduralXylazinePropranolol