MorphineEnkephalinsReceptors, Opioid, muEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Analgesics, OpioidEnkephalin, MethionineEnkephalin, LeucineMorphine DependenceEnkephalin, D-Penicillamine (2,5)-Receptors, Opioid, deltaNaloxoneNarcotic AntagonistsReceptors, Opioid, kappaNarcoticsDrug ToleranceNaltrexoneEnkephalin, Leucine-2-AlanineReceptors, OpioidMorphine DerivativesSubstance Withdrawal SyndromeEndorphinsPain MeasurementDose-Response Relationship, DrugLocus CoeruleusReceptors, Neurokinin-3LevallorphanPeriaqueductal GrayRats, Sprague-DawleyEthylketocyclazocineNeurokinin BOpioid PeptidesCyclazocineTachykininsReceptors, TachykininAnalgesiaD-Ala(2),MePhe(4),Met(0)-ol-enkephalinNucleus AccumbensPainSubstance PNeurokinin ABehavior, AnimalReceptors, Neurokinin-2HyperalgesiaDynorphinsAdenylate CyclaseNeuronsTime FactorsBrainSpinal CordCyclic AMPOpioid-Related DisordersBenzomorphansArrestinsAnalgesicsDopamine AgonistsCyclic AMP-Dependent Protein KinasesMice, Inbred C57BLInjections, SpinalRats, WistarBenzeneacetamidesG Protein-Coupled Inwardly-Rectifying Potassium ChannelsDrug Administration ScheduleGuinea PigsMotor ActivityRNA, Transfer, GlyMorphinansbeta-EndorphinEtorphineDiprenorphineRNA, MessengerCarboxypeptidase HGTP-Binding Protein beta SubunitsSynaptic TransmissionExcitatory Postsynaptic PotentialsReceptors, N-Methyl-D-AspartateMice, KnockoutOligopeptidesPiperidinesNeurokinin-1 Receptor AntagonistsSignal TransductionExcitatory Amino Acid AntagonistsGlycineInhibitory Postsynaptic PotentialsCodeineGABA AgonistsPyrrolidinesAnalysis of VarianceReceptors, Neurokinin-1Amino Acid SequencePain, PostoperativePhosphorylationFentanylInjections, IntraventricularMolecular Sequence DataPurinergic P1 Receptor AgonistsKineticsDrug InteractionsGene Expression RegulationThiorphanIleum