title: Transcutaneous electrical nerve stimulation attenuates postsurgical allodynia and suppresses spinal substance P and proinflammatory cytokine release in rats.
abstract: BACKGROUND
  Transcutaneous electrical nerve stimulation (TENS) is often used for management of chronic pain.
  
  
  OBJECTIVE
  The purpose of this study was to investigate whether TENS altered postincisional allodynia, substance P, and proinflammatory cytokines in a rat model of skin-muscle incision and retraction (SMIR).
  
  
  METHODS
  This was an experimental study.
  
  
  METHODS
  High-frequency (100-Hz) TENS therapy began on postoperative day 3 and was administered for 20 minutes daily to SMIR-operated rats by self-adhesive electrodes delivered to skin innervated via the ipsilateral dorsal rami of lumbar spinal nerves L1-L6 for the next 27 days. The expressions of substance P, tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1beta (IL-1β) in the spinal cord and mechanical sensitivity to von Frey stimuli (4g and 10g) were evaluated.
  
  
  RESULTS
  The SMIR-operated rats displayed a marked hypersensitivity to von Frey stimuli on postoperative day 3. In contrast to the SMIR-operated rats, SMIR-operated rats after TENS administration showed a quick recovery of mechanical hypersensitivity. On postoperative days 3, 16, and 30, SMIR-operated rats exhibited an upregulation of substance P and cytokines (TNF-α, IL-6, and IL-1β) in the spinal cord, whereas SMIR-operated rats after TENS therapy inhibited that upregulation. By contrast, the placebo TENS following SMIR surgery did not alter mechanical hypersensitivity and the levels of spinal substance P, TNF-α, IL-6, and IL-1β.
  
  
  CONCLUSIONS
  The experimental data are limited to animal models and cannot be generalized to postoperative pain in humans.
  
  
  CONCLUSIONS
  The results revealed that TENS attenuates prolonged postoperative allodynia following SMIR surgery. Increased levels of spinal substance P and proinflammatory cytokines, activated after SMIR surgery, are important in the processing of persistent postsurgical allodynia. The protective effect of TENS may be related to the suppression of spinal substance P and proinflammatory cytokines in SMIR-operated rats.
authors.affiliation: Y-W. Chen, PhD, Department of Physical Therapy, China Medical University, Taichung, Taiwan, and Department of Medical Research, Chi-Mei Medical Center, Tainan, Taiwan.
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Chen
authors.affiliation: J-I. Tzeng, MD, MS, Department of Food Sciences and Technology, Chia Nan University of Pharmacy and Science, Jen-Te, Tainan City, Taiwan, and Department of Anesthesiology, Chi-Mei Medical Center, Yong Kang, Tainan City, Taiwan.
authors.forename: Jann-Inn
authors.initials: JI
authors.lastname: Tzeng
authors.affiliation: M-F. Lin, MS, Department of Physical Therapy, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Min-Fei
authors.initials: MF
authors.lastname: Lin
authors.affiliation: C-H. Hung, PhD, Department of Physical Therapy, National Cheng Kung University, No. 1 Ta-Hsueh Road, Tainan, Taiwan. chhung@mail.ncku.edu.tw.
authors.forename: Ching-Hsia
authors.initials: CH
authors.lastname: Hung
authors.affiliation: J-J. Wang, PhD, MD, Department of Medical Research, Chi-Mei Medical Center, Tainan, Taiwan.
authors.forename: Jhi-Joung
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism*; D006930:Hyperalgesia / Q000517:prevention & control; D008297:Male; D023421:Models, Animal; D010149:Postoperative Pain / Q000517:prevention & control*; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D004561:Transcutaneous Electric Nerve Stimulation; D015854:Up-Regulation
chemical_list: D016207:Cytokines; D013373:Substance P