AnalgesicsAnalgesics, OpioidReceptors, Opioid, muReceptors, OpioidSleep, REMReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesAnalgesics, Non-NarcoticProgram EvaluationNarcotic AntagonistsMorphinePainAnalgesiaPain MeasurementNaloxoneSleep DeprivationOpioid-Related DisordersElectroencephalographyNaltrexoneSleepSleep StagesProgram DevelopmentWakefulnessPain, PostoperativeNarcoticsEnkephalinsTramadolEnkephalin, Ala(2)-MePhe(4)-Gly(5)-PharmacovigilanceBuprenorphineDrug ToleranceEndorphinsEnkephalin, D-Penicillamine (2,5)-FentanylDynorphinsPhenacetinElectromyographyBrain WavesAcetaminophenPain ThresholdHydromorphoneRats, Sprague-DawleyGovernment ProgramsElectrooculographyEnkephalin, LeucineTime FactorsMorphinansCodeineDextropropoxypheneMethadoneArousalInjections, SpinalPain ManagementEnkephalin, Leucine-2-AlanineHyperalgesiaAnti-Inflammatory Agents, Non-Steroidalbeta-EndorphinDose-Response Relationship, DrugUnited StatesMeperidinePentazocinePain, IntractableBenzeneacetamidesChronic PainRisk ManagementDiprenorphineRats, WistarAnesthetics, LocalButorphanolHydrocodoneHypothalamusPolysomnographyDouble-Blind MethodNational Health ProgramsOxymorphoneMorphine DerivativesAnalysis of VarianceAnalgesia, EpiduralDipyroneLevorphanolAnalgesia, Patient-ControlledPrescription DrugsBenzomorphansBupivacaineTreatment OutcomeHealth PromotionOxycodoneSubstance Withdrawal SyndromeHeroinNociceptorsAlfentanilCyclazocineNociceptionNalbuphineQuestionnairesBrain StemPyrrolidinesNeuralgiaBrain