title: d-Propoxyphene acts differently from morphine on opioid receptor-effector mechanisms.
abstract: The actions of d-propoxyphene and morphine on opioid receptor mechanisms were compared. In assay measuring receptor binding selectivity in vitro, with dihydromorphine, naloxone and an enkephalin analogue as radioactive ligands, d-propoxyphene differed from morphine in having a higher relative affinity for sites occupied by the peptide. Naloxone was more potent in antagonizing morphine- than d-propoxyphene-induced antinociception in the mouse hot-plate test. In morphine-tolerant mice showing three-fold lower morphine sensitivity the antinociceptive efficacy of d-propoxyphene was unchanged. The results indicate differences in receptor-effector mechanisms between d-propoxyphene and morphine.
mesh_terms: D000818:Animals; D011431:Dextropropoxyphene / Q000494:pharmacology*; D004090:Dihydromorphine / Q000494:pharmacology; D004361:Drug Tolerance; D005260:Female; D007700:Kinetics; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects*
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine; D004090:Dihydromorphine; D011431:Dextropropoxyphene