EndorphinsOpioid PeptidesReceptors, Opioidbeta-EndorphinEnkephalinsNaloxoneReceptors, Opioid, muAnalgesics, OpioidReceptors, Opioid, deltabeta-LipotropinReceptors, Opioid, kappaDynorphinsEnkephalin, LeucineEnkephalin, MethioninePeptidesNarcotic AntagonistsEnkephalin, Leucine-2-AlanineNaltrexoneAdrenocorticotropic HormoneEnkephalin, D-Penicillamine (2,5)-Enkephalin, Ala(2)-MePhe(4)-Gly(5)-NarcoticsMorphineD-Ala(2),MePhe(4),Met(0)-ol-enkephalinOligopeptidesOpioid-Related DisordersPeptide FragmentsMorphinansDiprenorphineAnalgesicsPainAmino Acid SequenceProtein PrecursorsBenzeneacetamidesMolecular Sequence DataPeptide LibraryBuprenorphineBenzomorphansDose-Response Relationship, DrugPyrrolidinesDrug TolerancePain MeasurementProtein BindingAnalgesiaAntimicrobial Cationic PeptidesPeptides, CyclicRats, Sprague-Dawley