EnkephalinsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Enkephalin, LeucineEnkephalin, MethionineReceptors, Opioid, muReceptors, OpioidAnalgesics, OpioidEnkephalin, D-Penicillamine (2,5)-Receptors, Opioid, deltaEnkephalin, Leucine-2-AlanineReceptors, Opioid, kappaEndorphinsNaloxoneNarcotic AntagonistsAnalgesicsMorphineOpioid PeptidesNaltrexonePain MeasurementReceptors, Neurokinin-3Injections, SpinalDynorphinsPainAnalgesiaCyclazocineDrug ToleranceEthylketocyclazocineNeurokinin Bbeta-EndorphinTachykininsNarcoticsReceptors, TachykininD-Ala(2),MePhe(4),Met(0)-ol-enkephalinInjections, IntraventricularDose-Response Relationship, DrugPain ThresholdMorphinansNociceptorsPeriaqueductal GrayBenzomorphansSubstance PBenzeneacetamidesAnalgesics, Non-NarcoticRats, Sprague-DawleyNeurokinin ASpinal CordOligopeptidesReceptors, Neurokinin-2NociceptionBuprenorphineHyperalgesiaPyrrolidinesDiprenorphinePiperidinesOpioid-Related DisordersMice, Inbred ICRFentanylMorphine DerivativesRNA, Transfer, GlyAdrenergic alpha-2 Receptor AgonistsGuinea PigsNeurokinin-1 Receptor AntagonistsPentazocineCarboxypeptidase HMicroinjectionsDrug InteractionsMorphine DependenceButorphanolBehavior, AnimalNociceptive PainReceptors, Adrenergic, alpha-2Reaction TimeHot TemperatureFormaldehydeSubstance Withdrawal SyndromeBenzylidene CompoundsMedulla OblongataReceptors, Neurokinin-1Adrenergic alpha-AgonistsClonidineSomatostatinBrainMethadoneRats, WistarGuanosine 5'-O-(3-Thiotriphosphate)CannabinoidsProtein PrecursorsGlycineAlfentanilLocus CoeruleusRadioligand AssayOxymorphoneAmino Acid SequenceDronabinolTailThiorphanLoperamideNeprilysinEtorphineVas Deferens