MorphineMorphine DependenceMorphine DerivativesAnalgesics, OpioidDrug ToleranceCircadian RhythmNarcoticsNaloxonePhotoperiodGalaxiesAstronomical ProcessesIslamReceptors, Opioid, muNarcotic AntagonistsSongbirdsSeasonal Affective DisorderVocalization, AnimalAnalgesiaInjections, SpinalPain MeasurementLightingCodeineLightSubstance Withdrawal SyndromePain, PostoperativeAnalgesicsPainReceptors, OpioidNaltrexoneAnalgesia, Patient-ControlledNalorphineDose-Response Relationship, DrugTime FactorsHeroinHydromorphoneFentanylEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Periaqueductal GrayBiological ClocksPhototherapyRats, Sprague-DawleyCircadian ClocksOxycodonePentazocineMorphinansEnkephalinsSleepNalbuphineReceptors, Opioid, deltaDarknessFossilsMelatoninMeperidineThebaineFeeding BehaviorSkin TemperaturePain ThresholdOxymorphoneAnalgesia, EpiduralBehavior, AnimalSeasonsOpiumEndorphinsMethadoneReceptors, Opioid, kappaInjections, SubcutaneousSpinal CordDrug InteractionsEcosystemInjections, IntraventricularArabidopsis ProteinsPapaverDouble-Blind MethodLevallorphanLocus CoeruleusArabidopsisHyperalgesiaBiological EvolutionPain, IntractableEtorphineTramadolBupivacaineInjections, IntravenousPhylogenyPruritusClonidineBuprenorphine