Studies on action mechanisms of morphine and 1-methadone in mice.
Chronically administered morphine and 1-methadone has previously been shown to yield different cross-tolerance patterns in mice. It was therefore tested if the two drugs differ in selectivities towards opioid binding sites in mouse brain membranes. Morphine and 1-methadone were found to show almost identical binding selectivities in vitro. It is suggested that the two drugs act by the same receptor(s), and that the observed asymmetry in cross-tolerance patterns could be due to differences in the receptor reserve for morphine- and 1-methadone-induced antinociception in mice.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D004361:Drug Tolerance; D066298:In Vitro Techniques; D008297:Male; D008691:Methadone / Q000494:pharmacology*; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects; D011957:Receptors, Opioid / Q000187:drug effects* / Q000378:metabolism
D011957:Receptors, Opioid; D009020:Morphine; D008691:Methadone