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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.
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Lars Terenius (1973) studied this question.
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