Fedotozine (INN; Jo-1196) is an opioid drug of the arylacetamide series which acts as a peripherally-specific, selective κ1-opioid receptor agonist with preference for the κ1A subtype. It was under investigation for the treatment of gastrointestinal conditions like irritable bowel syndrome and functional dyspepsia and made it to phase III clinical trials, but ultimately development was discontinued and it was never marketed. Receptor binding of the opioid receptor antagonist, [3H]diprenorphine, which has a similar affinity to the various opioid receptor subtypes, was characterized in subcellular fractions derived from either longitudinal or circular smooth muscle of the canine small intestine with their plexuses attached. The distribution of opioid binding activity showed a good correlation in the different fractions with the binding of the neuronal marker [3H]saxitoxin but no correlation to the smooth muscle plasma membrane marker 5'-nucleotidase.
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