MorphineMorphine DependenceMorphine DerivativesAnalgesics, OpioidDrug ToleranceNarcoticsVapor PressureNaloxoneDichelobacter nodosusReceptors, Opioid, muNarcotic AntagonistsAnalgesiaInjections, SpinalPain MeasurementSubstance Withdrawal SyndromeCodeinePain, PostoperativeAnalgesicsPainReceptors, OpioidNaltrexoneDose-Response Relationship, DrugAnalgesia, Patient-ControlledNalorphineRats, Sprague-DawleyHeroinHydromorphoneSteamFentanylEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Periaqueductal GrayGasesOxycodonePentazocineMorphinansEnkephalinsNalbuphineReceptors, Opioid, deltaMercuryMeperidineThebaineBehavior, AnimalPain ThresholdOxymorphoneAnalgesia, EpiduralOpiumEndorphinsHumidityTime FactorsSpinal CordReceptors, Opioid, kappaMethadoneMolecular Sequence DataInjections, SubcutaneousDrug InteractionsInjections, IntraventricularMercury PoisoningPapaverDouble-Blind MethodLevallorphanLocus CoeruleusHyperalgesiaPain, IntractableEtorphineTramadolBupivacaineInjections, IntravenousPruritusMiosisClonidineBuprenorphine