Effects of Cervical Sympathectomy on Mechanical Allodynia and Cold Allodynia in a Rat Model of Neuropathic Pain

Lee, Jai Min; Moon, Dong Eon; Park, Chong Min; Lee, Yoon Ki; Choi, Jun Whan; Yang, Nae Yun; Kim, Chang Sung; Kim, Sung Nyeun

Abstract

BACKGROUND: The pathophysiologic mechanism of the neuropathic pain is still unclear. We designed this study to evaluate the effect of bilateral cervical sympathectomy on allodynia and the relationship of neuropathic pain with sympathetic nerve system of supraspinal level in rats experiencing neuropathic pain.
METHODS
Neuropathic pain was produced by tight ligating the left 5th and 6th lumbar spinal nerves of male Sprague-Dawley rats. Mechanical allodynia was quantified by measuring the foot withdrawal frequency to stimuli with two von Frey filaments of 14.5 mN and 53.9 mN applied to the affected left hind paw, and cold allodynia was quantified with the same manner using 100% acetone. We divided the neuropathic pain models into experimental group (bilateral cervical sympathectomy) and control group (sham operation), and then measured the foot withdrawal frequency 1, 3, 5, 7, 14, 21 and 28 days postoperatively.
RESULTS
In experimental group, the foot withdrawal frequency to mechanical stimuli with 14.5 and 53.9 mN of von Frey filament and cold stimuli with 100% acetone was significantly lower than that of control group for all postoperative observation points. Also, the experimental group showed decrease in foot withdrawal frequency compared with preoprative value over the course of the study.
CONCLUSIONS
Bilateral cervical sympathectomy reduced mechanical allodynia and cold allodynia in the rat model of neuropathic pain suggesting that neuropathic pain, although the lesions are localized in low extremities, may be correlated with functional disturbance of sympathetic nerve fibers of supraspinal or brain level and help explain the mechanism of neuropathic pain.