Receptors, Invertebrate PeptideReceptors, OpioidInvertebratesDihydromorphineNaloxoneEnkephalin, Leucine-2-AlanineEnkephalinsEndorphinsEtorphinePeptidesEnkephalin, LeucineEthylketocyclazocineEnkephalin, MethionineDiprenorphineMorphineCyclazocineNarcoticsReceptors, Opioid, muLevorphanolBenzomorphansNaltrexoneNarcotic AntagonistsEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Morphine DerivativesReceptors, Opioid, deltaMorphinansOpiate AlkaloidsDynorphinsPhenazocineFentanylReceptors, Opioid, kappaDextrorphanPeptide Fragmentsbeta-EndorphinAnalgesics, OpioidEnkephalin, D-Penicillamine (2,5)-Amino Acid SequenceLevallorphanHybrid CellsBinding, CompetitiveBrainOpioid-Related DisordersPeptide LibraryAnalgesiaAnalgesicsMolecular Sequence DataOpioid PeptidesOligopeptidesAntimicrobial Cationic PeptidesLoperamideKineticsBrain ChemistryNeuroblastomaGuanylyl ImidodiphosphatePeptides, CyclicRats, Inbred StrainsVertebratesDose-Response Relationship, DrugIleumBase SequencePeptide MappingCodeineHeroinStructure-Activity RelationshipGliomaDrug ToleranceMethadoneGuinea PigsPyrrolidinesCell LineClonidineCell MembraneReceptors, DrugMolluscaAdenylate CyclaseKetamineSequence Homology, Amino AcidNatriuretic Peptide, BrainNeuronsPainHeroin DependenceOpiumStereoisomerismProtein BindingEchinodermataSubstance Withdrawal SyndromeDNA, ComplementarySubstance Abuse DetectionCrustaceaUrochordataReceptors, AdrenergicPhylogenyTime FactorsAquatic OrganismsRats, Sprague-DawleyVasoactive Intestinal PeptideChordata, NonvertebrateMorphine DependenceReceptors, Adrenergic, alphaBivalvia