AnalgesicsAnalgesics, OpioidReceptors, Opioid, muBenzodiazepinesDexmedetomidineAnalgesiaAnalgesics, Non-NarcoticFlumazenilPainReceptors, OpioidHypnotics and SedativesPain MeasurementFlunitrazepamDiazepamMorphineReceptors, GABA-ANaloxoneAnti-Anxiety AgentsReceptors, Opioid, deltaPain ThresholdReceptors, Opioid, kappaBenzodiazepinonesHyperalgesiaGABA ModulatorsOpioid PeptidesKetamineFlurazepamDose-Response Relationship, DrugLorazepamCarbolinesRats, Sprague-DawleyGABA-A Receptor AgonistsBehavior, AnimalPlant ExtractsNarcotic AntagonistsMidazolamClonazepamOpioid-Related DisordersChlordiazepoxideDrug ToleranceAlprazolamIsoquinolinesNaltrexoneSubstance Withdrawal SyndromeTriazolamNarcoticsGABA-A Receptor AntagonistsPain, PostoperativeConvulsantsEnkephalinsTramadolBuprenorphineNitrazepamEnkephalin, Ala(2)-MePhe(4)-Gly(5)-NordazepamMuscimolEndorphinsEnkephalin, D-Penicillamine (2,5)-FentanylOxazepamgamma-Aminobutyric AcidDiazepam Binding InhibitorPentylenetetrazoleTemazepamDynorphinsPhenacetinBrainAcetaminophenGABA AgonistsHydromorphoneEnkephalin, LeucineRadioligand AssayMorphinansMethadoneDextropropoxypheneCodeinePentobarbitalAnticonvulsantsDouble-Blind MethodReceptors, GABAInjections, SpinalDrug InteractionsEnkephalin, Leucine-2-Alaninebeta-EndorphinAnti-Inflammatory Agents, Non-SteroidalSeizuresClorazepate DipotassiumMeperidinePain ManagementDrug UtilizationPentazocinePyridazinesLigandsCyclazocineAzabicyclo CompoundsBenzeneacetamidesPregnanolonePain, IntractableDiprenorphineBarbiturates