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3-Methoxynaltrexone, a selective heroin/morphine-6beta-glucuronide antagonist
1The Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
FEBS Letters
|July 21, 1997
Summary
A novel mu opioid receptor subtype mediates the analgesic effects of heroin and morphine-6beta-glucuronide (M6G). 3-methoxynaltrexone selectively antagonizes these actions, offering potential for opioid abuse therapeutics.
Area of Science:
- Pharmacology
- Neuroscience
- Medicinal Chemistry
Background:
- Recent research suggests heroin and M6G act via a distinct mu opioid receptor subtype.
- This receptor site exhibits high affinity for 3H-M6G and is selectively antagonized by 3-methoxynaltrexone.
Purpose of the Study:
- To investigate the specific opioid receptor subtype involved in heroin and M6G analgesia.
- To determine the selectivity of 3-methoxynaltrexone as an antagonist for these actions.
Main Methods:
- In vivo antagonism studies using 3-methoxynaltrexone in rodent models.
- Radioligand binding assays to characterize the 3H-M6G binding site.
- Dose-response analyses of heroin, M6G, and morphine analgesia.
Main Results:
- 3-methoxynaltrexone selectively antagonized the analgesic effects of heroin and M6G.
- This antagonism occurred without affecting analgesia mediated by morphine, enkephalins, or other opioid receptor subtypes.
- Dose-response studies confirmed 3-methoxynaltrexone's selective blockade of heroin and 6-acetylmorphine, but not morphine, analgesia.
Conclusions:
- 3-methoxynaltrexone selectively blocks a novel 3H-M6G binding site responsible for heroin and M6G analgesia.
- This selective antagonism highlights a unique opioid pathway for heroin and M6G.
- The findings suggest potential therapeutic applications for 3-methoxynaltrexone in managing opioid abuse.