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Updated: Sep 5, 2025
The Sciatic Nerve Cuffing Model of Neuropathic Pain in Mice
Published on: July 16, 2014
Preventive Intrathecal Injection of Bupivacaine Alleviated Microglia Activation and Neuropathic Pain in a Rat Model
Chih-Cheng Wu1,2,3, Cheng-Yi Chang4,5, Chung-Yuh Tzeng6,7
1Department of Anesthesiology, Taichung Veterans General Hospital, Taichung City 407, Taiwan.
Abstract:
Spinal microglia are crucial to neuronal hyper-excitability and pain hypersensitivity. The local anesthetic bupivacaine is commonly used for both peripheral and spinal anesthesia. The pain-relief effects resulting from the peripheral and systemic administration of bupivacaine have been previously reported. In this study, the preventive effects of intrathecal bupivacaine administration against neuropathic pain were revealed in a rat model of sciatic nerve chronic constriction injury (CCI). Using a CCI rat model, pain hypersensitivity, characterized by mechanical allodynia and thermal hyperalgesia, correlated well with microglia M1 polarization, activation and pro-inflammatory cytokine expression in both spinal cord dorsal horns and sciatic nerves. Bupivacaine attenuated pain behaviors and inflammatory alternations. We further identified that the Interferon Regulatory Factor 5 (IRF5)/P2X Purinoceptor 4 (P2X4R) and High Mobility Group Box 1 (HMGB1)/Toll-Like Receptor 4 (TLR4)/NF-κB inflammatory axes may each play pivotal roles in the acquisition of microglia M1 polarization and pro-inflammatory cytokine expression under CCI insult. The relief of pain paralleled with the suppression of microglia M1 polarization, elevation of microglia M2 polarization, and inhibition of IRF5/P2X4R and HMGB1/TLR4/NF-κB in both the spinal cord dorsal horns and sciatic nerve. Our findings provide molecular and biochemical evidence for the anti-neuropathic effect of preventive bupivacaine.
Insights
Preventive intrathecal bupivacaine reduced neuropathic pain in rats by suppressing spinal microglia activation. This treatment inhibited key inflammatory pathways, offering a novel approach to managing nerve injury pain.
Area of Science:
- Neuroscience
- Immunology
- Pharmacology
Background:
- Spinal microglia play a key role in pain hypersensitivity.
- Bupivacaine is a local anesthetic with known pain-relief effects.
- Neuropathic pain mechanisms involving microglia require further elucidation.
Purpose of the Study:
- To investigate the preventive effects of intrathecal bupivacaine on neuropathic pain in a rat model.
- To explore the molecular mechanisms underlying bupivacaine's anti-neuropathic effects, focusing on microglia polarization and inflammatory pathways.
Main Methods:
- A rat model of sciatic nerve chronic constriction injury (CCI) was established.
- Pain behaviors (mechanical allodynia, thermal hyperalgesia) were assessed.
- Microglia polarization (M1/M2), pro-inflammatory cytokine expression, and specific inflammatory axes (IRF5/P2X4R, HMGB1/TLR4/NF-κB) were analyzed in the spinal cord and sciatic nerve.
Main Results:
- CCI induced pain hypersensitivity, correlating with M1 microglia polarization and increased pro-inflammatory cytokines.
- Intrathecal bupivacaine attenuated pain behaviors and reduced M1 microglia polarization while increasing M2 polarization.
- Bupivacaine inhibited the IRF5/P2X4R and HMGB1/TLR4/NF-κB inflammatory pathways.
Conclusions:
- Preventive intrathecal bupivacaine effectively reduces neuropathic pain in a CCI rat model.
- The anti-neuropathic effect is mediated by the suppression of M1 microglia polarization and key inflammatory signaling pathways.
- Findings support bupivacaine as a potential therapeutic agent for preventing neuropathic pain.
