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Updated: Jul 16, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
07:23

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities

Published on: July 29, 2014

Morphine-3-glucuronide inhibits morphine induced, but enhances morphine-6-glucuronide induced locomotor activity in

Marte Handal1, Ase Ripel, Tor Aasmundstad

  • 1Norwegian Institute of Public Health, Division of Forensic Toxicology and Drug Abuse, Nydalen, NO-0403 Oslo, Norway. marte.handal@fhi.no

Pharmacology, Biochemistry, and Behavior
|March 9, 2007
PubMed

Insights

Morphine metabolite morphine-3-glucuronide (M3G) affects morphine and morphine-6-glucuronide (M6G) differently. M3G reduces morphine

Area of Science:

  • Pharmacology
  • Neuroscience
  • Drug Metabolism

Background:

  • Morphine-3-glucuronide (M3G) is a primary morphine metabolite lacking opioid activity.
  • M3G may antagonize morphine and morphine-6-glucuronide (M6G) effects.
  • The influence of M3G on psychostimulant properties of morphine and M6G requires investigation.

Purpose of the Study:

  • To investigate the impact of M3G on the psychostimulant effects of morphine and M6G.
  • To elucidate the pharmacokinetic and pharmacodynamic interactions between M3G, morphine, and M6G.

Main Methods:

  • Mice received M3G or saline followed by morphine or M6G.
  • Locomotor activity was measured to assess psychostimulant properties.
  • Brain and serum concentrations of morphine and M6G were analyzed.

Main Results:

  • M3G reduced morphine-induced locomotor activity in a concentration-dependent manner.
  • M3G did not significantly alter brain morphine concentrations, indicating pharmacodynamic interaction.
  • M3G increased M6G-induced locomotor activity and M6G concentrations, suggesting pharmacokinetic interaction.

Conclusions:

  • M3G exhibits complex interactions with morphine and M6G regarding locomotor activity.
  • These findings suggest M3G influences drug reward mechanisms.
  • Pharmacokinetic and pharmacodynamic factors mediate M3G's differential effects on morphine and M6G.

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