PenicillamineEnkephalinsReceptors, Opioid, deltaEnkephalin, LeucineEnkephalin, MethionineEnkephalin, Leucine-2-AlanineEnkephalin, D-Penicillamine (2,5)-Receptors, Opioid, muEnkephalin, Ala(2)-MePhe(4)-Gly(5)-Receptors, OpioidGold Sodium ThiomalateAnalgesics, OpioidReceptors, Opioid, kappaHepatolenticular DegenerationNaltrexoneNarcotic AntagonistsOpioid PeptidesEndorphinsS-Nitroso-N-AcetylpenicillamineNaloxoneSulfasalazineDiprenorphineAurothioglucoseArthritis, RheumatoidAuranofinTartratesNarcoticsCystinuriaMorphineDimercaprolDynorphinsBenzomorphansDrug Eruptionsbeta-EndorphinChelating AgentsOrganogold CompoundsBlood SedimentationAntimonyMorphinansAnalgesicsOligopeptidesNitric Oxide DonorsSulfhydryl CompoundsAminopropionitrileEtorphineDose-Response Relationship, DrugMyasthenia GravisCopperDrug ToleranceBenzeneacetamidesSchistosomicidesGoldEthylketocyclazocinePyrrolidinesCyclazocineBenzamidesAzathioprinePainOpioid-Related DisordersFentanylGuanosine 5'-O-(3-Thiotriphosphate)Rats, Sprague-DawleyPain MeasurementMorphine DerivativesPiperazinesTime FactorsLigandsNitric OxideProteinuriaD-Ala(2),MePhe(4),Met(0)-ol-enkephalinTetrahydroisoquinolines