MorphineMethadoneEnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Morphine DependenceEnkephalin, MethionineEnkephalin, LeucineNarcoticsAnalgesics, OpioidReceptors, Opioid, muDrug ToleranceMorphine DerivativesNaloxoneEnkephalin, D-Penicillamine (2,5)-Enkephalin, Leucine-2-AlanineNarcotic AntagonistsReceptors, OpioidSubstance Withdrawal SyndromeReceptors, Opioid, deltaEndorphinsOpioid-Related DisordersNaltrexoneOpiate Substitution TreatmentLocus CoeruleusLevallorphanPeriaqueductal GrayReceptors, Neurokinin-3AnalgesiaHeroin DependencePain MeasurementRats, Sprague-DawleyDose-Response Relationship, DrugPainEthylketocyclazocineCyclazocineOpioid PeptidesNeurokinin BHeroinMethadyl AcetateBuprenorphineReceptors, Opioid, kappaTachykininsReceptors, TachykininInjections, SpinalAnalgesicsNucleus AccumbensCodeineD-Ala(2),MePhe(4),Met(0)-ol-enkephalinBehavior, AnimalSubstance PHyperalgesiaTime FactorsNeonatal Abstinence SyndromeNeurokinin ADynorphinsSpinal CordPain, PostoperativeDrug Administration ScheduleBrainReceptors, Neurokinin-2PyrrolidinesNeuronsMorphinansAdenylate CyclaseDiprenorphineBenzomorphansSubstance Abuse DetectionFentanylHydromorphoneNalorphineMotor ActivityArrestinsEtorphinebeta-EndorphinG Protein-Coupled Inwardly-Rectifying Potassium ChannelsOpiumDrug InteractionsRNA, Transfer, GlyCyclic AMPMice, Inbred C57BLCyclic AMP-Dependent Protein KinasesOxycodonePentazocineRats, WistarAnalgesia, Patient-ControlledBenzeneacetamidesGuinea PigsReceptors, N-Methyl-D-AspartateCarboxypeptidase HGTP-Binding Protein beta SubunitsRNA, MessengerAnalysis of VarianceMeperidineInjections, IntraventricularExcitatory Postsynaptic PotentialsPain ThresholdMice, KnockoutSynaptic TransmissionDrug OverdoseNeurokinin-1 Receptor Antagonists