Related Experiment Video

Updated: Mar 27, 2026

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

Published on: July 29, 2014

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A mu-opioid receptor positive allosteric modulator provides opioid-sparing antinociception without enhancing opioid

Kelsey E Kochan1, Benjamin M Clements1, Thomas D Prince1

  • 1Department of Pharmacology, Edward F Domino Research Center, University of Michigan, Ann Arbor, Michigan.

The Journal of Pharmacology and Experimental Therapeutics
|March 24, 2026
PubMed

Insights

A novel mu-opioid receptor (MOR) modulator enhances pain relief from opioid drugs without increasing side effects like constipation or respiratory depression, offering a safer pain management strategy.

Area of Science:

  • Pharmacology
  • Neuroscience
  • Pain Management

Background:

  • Mu-opioid receptor (MOR) agonists are effective analgesics but cause significant adverse effects, including addiction and respiratory depression.
  • There is a critical need for safer pain management strategies to address undertreated pain and opioid addiction.
  • Positive allosteric modulators (PAMs) of MOR offer a potential alternative by enhancing receptor function without direct activation.

Purpose of the Study:

  • To investigate the effects of the MOR PAM, 2-(3-bromo-4-methoxyphenyl)-3-[(4-chlorophenyl) sulfonyl]-thiazolidine, on the behavioral actions of opioid drugs.
  • To determine if this MOR PAM can enhance opioid-induced analgesia while mitigating adverse effects.

Main Methods:

  • Utilized in vivo mouse models to assess antinociception for acute and inflammatory pain.
  • Evaluated adverse effects including constipation, respiratory depression (via blood oxygen levels and respiration rate), and reward (conditioned place preference).
  • Administered the MOR PAM in conjunction with standard opioid drugs like morphine and fentanyl.

Main Results:

  • The MOR PAM significantly enhanced opioid drug-induced antinociception in both acute and inflammatory pain models.
  • Crucially, the PAM did not enhance opioid-induced constipation, respiratory depression, or reward-seeking behavior.
  • These findings indicate a dissociation between analgesia and adverse effects when using this MOR PAM.

Conclusions:

  • 2-(3-bromo-4-methoxyphenyl)-3-[(4-chlorophenyl) sulfonyl]-thiazolidine acts as a safe opioid-sparing agent by potentiating analgesia.
  • MOR PAMs demonstrate potential for improved pain management, offering efficacy without the typical opioid side effect profile.
  • This research supports the development of MOR PAMs as a novel therapeutic strategy for pain relief.
Keywords:
Allosteric modulatorAntinociceptionConstipationMu-opioid receptorRespiratory depressionReward

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