Stereospecific Uptake of Narcotic Analgesics by a Subcellular Fraction of the Guinea-pig Ileum

Abstract

Longitudinal muscle of guinea-pig ileum was homogenized. Precipitates from centrifugation were incubated with labelled dihydromorphine and competitors. The uptake of label to a high-speed fraction was stereospecific (the analgesics levorphanol and levo-methadone were more active competitors than their inactive dextro-counterparts). Morphine, normorphine, dextromoramide, the antagonists nalorphine and naloxone inhibited uptake. Codeine was inactive.