SPECIFIC AFFINITY LABELING OF MU-OPIOID RECEPTORS IN RAT-BRAIN BY S-ACTIVATED SULFHYDRYLDIHYDROMORPHINE ANALOGS

S-Activated sulfhydryldihydromorphine analogs 1 and 2 were synthesized . In the rat brain receptor binding assays, both 1 and 2 exhibited con siderably high affinities for mu opioid receptors (IC50; 1 = 31.1 nM, 2 = 10.7 nM). However, when each analog was incubated with membranes f or the purpose of getting disulfide bridgings, 1 (EC(50) = 58 nM) was found to affinity-label the mu receptors about 30 times more effective ly than 2 (EC(50) = 1700 nM).