Stereospecific Binding of the Potent Narcotic Analgesic [3H]Etorphine to Rat-Brain Homogenate

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RESUMO

Etorphine, the most potent narcotic analgesic known, was labeled with tritium by catalytic exchange. This drug exhibits stereospecific, saturable binding to rat-brain homogenate. At saturation, the stereospecific binding is 0.1-0.15 pmol/mg of protein. Specific binding is inhibited high salt concentrations, sulfhydryl reagents, and proteolytic enzymes, but is unaffected by phospholipases A and C, sodium azide, sodium fluoride, and prostaglandins E1 and E2. Competition for binding of [3H]etorphine correlates with agonist and antagonist potencies. The stable, stereospecific binding of an active narcotic analgesic supports the existence of opiate receptors.

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