LIU Kun¹, ZHI Mujun², ZHENG Zhouli³, HE Xun¹, SUN Guang², ZHANG Meng⁴, GAO Xinyan¹, ZHU Bing¹

(1 Department of Physiology, Institute of Acupuncture and Moxibustion, China Academy of  Chinese Medical Sciences, Beijing, People’s Republic of China; 2 College of Acupuncture and Moxibustion, Changchun University of Chinese Medicine, Changchun, People’s Republic of China; 3 College of Acupuncture and Moxibution, Shaanxi University of Chinese Medicine, People’s Republic of China; 4 Department of   Chinese Medicine, Dongli Hospital of Traditional  

Chinese Medicine, Tianjin, People’s Republic of China)

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  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 analgesiaon chronic neuropathic pain and the underlying mechanisms. 

Key words: neuropathic pain, chronic constriction injury, acupuncture, analgesia, C-fiber reflex