Receptors, OpioidReceptors, Opioid, muReceptors, Opioid, deltaReceptors, Opioid, kappaSigma FactorAnalgesics, OpioidNarcotic AntagonistsOpioid PeptidesNaltrexoneNaloxoneEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Receptors, sigmaEnkephalin, D-Penicillamine (2,5)-EnkephalinsDiprenorphineMorphineDynorphinsEnkephalin, Leucine-2-AlanineEnkephalin, LeucineBenzeneacetamidesNarcoticsMorphinansRNA Polymerase Sigma 54BenzomorphansAnalgesicsEndorphinsEtorphinebeta-EndorphinPyrrolidinesDiterpenes, ClerodaneOpioid-Related DisordersEthylketocyclazocineCyclazocineBenzylidene CompoundsDrug ToleranceLevorphanolPainFentanylPain MeasurementBuprenorphineEnkephalin, MethionineAnalgesiaOligopeptidesDose-Response Relationship, DrugDNA-Directed RNA PolymerasesRats, Sprague-DawleyMorphine DerivativesPentazocineGuanosine 5'-O-(3-Thiotriphosphate)ButorphanolGene Expression Regulation, BacterialHeroinLigandsPhenazocineRadioligand AssaySubstance Withdrawal SyndromeMorphine DependenceMolecular Sequence DataInjections, SpinalPeriaqueductal GrayBacterial ProteinsMethadoneLoperamideCHO CellsSomatostatinHyperalgesiaBinding, CompetitivePain ThresholdNociceptorsAmino Acid SequenceAnalgesics, Non-NarcoticOpiate AlkaloidsSalviaSpinal CordCricetinaeHydromorphoneInjections, IntraventricularBacillus subtilisCricetulusGuinea PigsSpiro CompoundsBehavior, AnimalD-Ala(2),MePhe(4),Met(0)-ol-enkephalinAzocinesTranscription, GeneticBase SequenceBrainDrug InteractionsPromoter Regions, GeneticPiperidinesG-Protein-Coupled Receptor Kinase 3DihydromorphineRats, WistarArrestinsHeroin DependenceStructure-Activity Relationship14-3-3 ProteinsGTP-Binding ProteinsProtein BindingMicroinjections