AnalgesicsAnalgesics, OpioidReceptors, Opioid, muReceptors, OpioidSubstance Withdrawal SyndromeSleep, REMReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesAnalgesics, Non-NarcoticMorphineNaloxonePainNarcotic AntagonistsAnalgesiaPain MeasurementOpioid-Related DisordersSleep DeprivationElectroencephalographySleepNaltrexoneDrug ToleranceSleep StagesWakefulnessEnkephalinsPain, PostoperativeEnkephalin, Ala(2)-MePhe(4)-Gly(5)-TramadolMorphine DependenceNarcoticsAlcohol Withdrawal DeliriumAlcohol Withdrawal SeizuresRats, Sprague-DawleyPharmacovigilanceBuprenorphineEndorphinsFentanylEnkephalin, D-Penicillamine (2,5)-Pain ThresholdDynorphinsDose-Response Relationship, DrugHyperalgesiaElectromyographyAcetaminophenPhenacetinDextropropoxypheneHydromorphoneBrain WavesTime FactorsInjections, SpinalMorphinansCodeineElectrooculographyEnkephalin, LeucineMethadoneArousalRats, WistarAnti-Inflammatory Agents, Non-Steroidalbeta-EndorphinEnkephalin, Leucine-2-AlaninePentazocinePain ManagementDouble-Blind MethodMeperidineBehavior, AnimalBenzeneacetamidesHeroinPain, IntractableDiprenorphineButorphanolAnesthetics, LocalHypothalamusChronic PainAnalysis of VarianceEthanolPolysomnographyHydrocodoneMorphine DerivativesNociceptorsOxymorphoneBenzomorphansAnalgesia, EpiduralOxycodoneBrainRisk ManagementDipyroneLevorphanolNociceptionAnalgesia, Patient-ControlledBupivacaineDisease Models, AnimalWithholding TreatmentNeuralgiaCarrageenanPyrrolidinesBrain StemAlfentanilCyclazocineNalbuphineDrug Interactions