AnalgesicsAnalgesics, OpioidReceptors, Opioid, muReceptors, OpioidSleep, REMReceptors, Opioid, deltaReceptors, Opioid, kappaOpioid PeptidesSoftwareAnalgesics, Non-NarcoticMorphineNarcotic AntagonistsPainAnalgesiaNaloxonePain MeasurementSleep DeprivationInternetOpioid-Related DisordersAlgorithmsElectroencephalographyNaltrexoneSleepSleep StagesHigh-Throughput Nucleotide SequencingWakefulnessPain, PostoperativeEnkephalinsTramadolNarcoticsComputer GraphicsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-User-Computer InterfaceDrug TolerancePharmacovigilanceGenomicsBuprenorphineEndorphinsComputational BiologyEnkephalin, D-Penicillamine (2,5)-FentanylProgramming LanguagesDynorphinsPhenacetinDatabases, GeneticBrain WavesAcetaminophenElectromyographySequence Analysis, DNAPain ThresholdHydromorphoneElectrooculographyRats, Sprague-DawleyEnkephalin, LeucineMorphinansDextropropoxypheneCodeineArousalInjections, SpinalEnkephalin, Leucine-2-AlanineHyperalgesiabeta-EndorphinAnti-Inflammatory Agents, Non-SteroidalMeperidinePain ManagementPentazocineDose-Response Relationship, DrugMethadoneBenzeneacetamidesPain, IntractableDiprenorphineRats, WistarButorphanolAnesthetics, LocalHydrocodoneChronic PainHypothalamusPolysomnographyOxymorphoneTime FactorsMorphine DerivativesRisk ManagementDouble-Blind MethodDipyroneAnalgesia, EpiduralLevorphanolAnalgesia, Patient-ControlledBenzomorphansBupivacaineModels, StatisticalOxycodoneNociceptorsAlfentanilCyclazocineSequence AlignmentNociceptionNalbuphineSubstance Withdrawal SyndromePrescription DrugsBrain Stem