title: 3-Methoxynaltrexone, a selective heroin/morphine-6beta-glucuronide antagonist.
abstract: Recent work has suggested that heroin and morphine-6beta-glucuronide (M6G) both act through a novel mu opioid receptor subtype distinct from those mediating morphine's actions. This very high affinity 3H-M6G site is selectively competed by 3-methoxynaltrexone. In vivo, 3-methoxynaltrexone (2.5 ng, i.c.v.) selectively antagonizes the analgesic actions of heroin and M6G without interfering with mu (morphine and [D-Ala2,MePhe4,Gly(ol)5]enkephalin), delta ([D-Pen2,D-Pen5]enkephalin), kappa1 (U50,488H) or kappa3 (naloxone benzoylhydrazone) analgesia. In dose-response studies, 3-methoxynaltrexone (2.5 ng, i.c.v.) significantly shifted the ED50 values for heroin and its active metabolite, 6-acetylmorphine, without affecting the morphine curve. These results indicate that 3-methoxynaltrexone selectively blocks a novel 3H-M6G binding site which is responsible for the analgesic actions of heroin and M6G. This ability to selectively antagonize heroin actions opens new possibilities in the development of therapeutics for the treatment of opioid abuse.
authors.affiliation: The Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
authors.forename: G P
authors.initials: GP
authors.lastname: Brown
authors.forename: K
authors.initials: K
authors.lastname: Yang
authors.forename: M A
authors.initials: MA
authors.lastname: King
authors.forename: G C
authors.initials: GC
authors.lastname: Rossi
authors.forename: L
authors.initials: L
authors.lastname: Leventhal
authors.forename: A
authors.initials: A
authors.lastname: Chang
authors.forename: G W
authors.initials: GW
authors.lastname: Pasternak
mesh_terms: D000698:Analgesia; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D016466:CHO Cells; D006224:Cricetinae; D003932:Heroin / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D008297:Male; D051379:Mice; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009022:Morphine Derivatives / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014316:Tritium
chemical_list: C107547:3-methoxynaltrexone; D009022:Morphine Derivatives; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D014316:Tritium; D009271:Naltrexone; C035349:morphine-6-glucuronide; D003932:Heroin; D009020:Morphine