Application of the chronic constriction injury of the partial sciatic nerve model to assess acupuncture analgesia

Abstract

Purpose

To validate and explore the application of a rat model of chronic constriction injury to the partial sciatic nerve in investigation of acupuncture analgesia.

Methods

Chronic constriction injury of the sciatic nerve (CCI) and chronic constriction injury of the partial sciatic nerve (CCIp) models were generated by ligating either the sciatic nerve trunk or its branches in rats. Both models were evaluated via paw mechanical withdrawal latency (PMWL), paw mechanical withdrawal threshold (PMWT), nociceptive reflex-induced electromyogram (C-fiber reflex EMG), and dorsal root ganglion immunohistochemistry. Electroacupuncture (EA) was performed at GB30 to study the analgesic effects on neuropathic pain and the underlying mechanisms.

Results

Following ligation of the common peroneal and tibial nerves, CCIp rats exhibited hindlimb dysfunction, hind paw shrinkage and lameness, mirroring those of CCI rats (generated by ligating the sciatic nerve trunk). Compared to presurgery measurements, CCIp and CCI modeling significantly decreased the PMWL and PMWT. EA at GB30 increased the PMWL and PMWT in both CCI and CCIp rats. Calcitonin gene-related polypeptide and substance P expressions were apparently increased in both CCI and CCIp groups, but were not different from each other. The C-fiber reflex EMG of the biceps femoris was preserved in CCIp rats, but it could not be recorded in CCI rats on the 5th day after nerve ligation. The C-fiber reflex EMG was reduced at 0, 1, and 2 minutes after EA in CCIp rats, but only at 0 and 1 minute after EA in normal rats.

Conclusion

The CCIp model is better than the CCI model for studying acupuncture analgesia on chronic neuropathic pain and the underlying mechanisms.

Keywords:

• neuropathic pain
• chronic constriction injury
• acupuncture
• analgesia
• C-fiber reflex

Acknowledgments

This work was supported by National Natural Science Foundation of China granted to Kun Liu (No. 81303054), Xin-yan Gao (No. 81473778), and Bing Zhu (No. 81130063), and grants from International Science & Technology Cooperation Program of China (Grant No. 2014DFG32700) and National Basic Research Program of China (973 Program, No. 2014CB543103). We thank Professor Yi-kuan Xie for his constructive suggestions during our experiment and Kristin Schoepfer for assistance with word polishing and grammar corrections.

Author contributions

All authors contributed toward data analysis, drafting and critically revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.