Related Experiment Video
Updated: Oct 23, 2025
07:23
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
33.7K
Microglial ablation does not affect opioid-induced hyperalgesia in rodents.
Xin Liu1, Bo-Long Liu1,2, Qing Yang1
1Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, United States.
Pain
|August 26, 2021
Summary
Challenging the role of microglia in opioid-induced hyperalgesia, this study found that removing these immune cells did not affect pain sensitivity in mice and rats. These findings question the established understanding of opioid pain mechanisms.
Area of Science:
- Neuroscience
- Immunology
- Pharmacology
Background:
- Opioid analgesics are primary pain relievers, but chronic use can paradoxically increase pain, reducing treatment efficacy.
- The exact mechanisms behind opioid-induced hyperalgesia (OIH) remain unclear.
- Microglia are widely suspected to be key players in OIH development.
Purpose of the Study:
- To investigate the role of microglia in the development of opioid-induced hyperalgesia.
- To determine if microglial ablation prevents or reduces OIH.
Main Methods:
- Microglial ablation was achieved using genetic (CD11b-diphtheria toxin receptor transgenic mice) and pharmacological (PLX5622) methods.
- Behavioral tests assessed mechanical and thermal hyperalgesia in male and female mice and rats.
- The impact of microglial depletion on morphine-induced hyperalgesia was evaluated.
Main Results:
- Effective microglial ablation did not impair the expression of morphine-induced hyperalgesia.
- These results were consistent across different methods of ablation, sexes, and species (mouse and rat).
Conclusions:
- The study challenges the widely held belief in microglia's critical role in OIH.
- Findings suggest that other mechanisms may be more significant in the development of opioid-induced hyperalgesia.
- Further research is needed to elucidate the precise pathways involved in OIH.
