Contralateral Electroacupuncture Relieves Chronic Neuropathic Pain in Rats with Spared Nerve Injury

BACKGROUND: Acupuncture and electroacupuncture (EA) are widely applied in the treatment of various conditions, including pain. Acupuncture stimulation is applied not only in areas close to pain sites, but also in distal regions or on the contralateral side of the body. Identifying which acupuncture paradigms produce best therapeutic effects is of clinical significance. MATERIAL/METHODS: Spared nerve injury (SNI) was applied to establish a rat model of neuropathic pain. We applied 14 sessions of EA (BL 60 and BL 40, 1–2 mA, and 2 Hz, 30 min per session) every other day from days 3 to 29 after surgery on the contralateral or ipsilateral side of pain. von Frey hair was applied to examine mechanical allodynia in the SNI model and analgesic effects of EA. All experimental procedures were approved by the Animal Care and Use Committee of our university, according to the guidelines of the International Association for the Study of Pain. RESULTS: SNI produced significant and long-lasting mechanical allodynia (p<0.001) in injured paws. Repeated EA on the contralateral side of the pain significantly attenuated mechanical allodynia from 14 days after surgery (p<0.05). By contrast, ipsilateral EA did not show analgesic effects (p>0.05). CONCLUSIONS: These findings indicate that contralateral EA is superior to local EA in some types of pain disorders. Further investigations are needed for a more comprehensive understanding of the central mechanisms of acupuncture.