High-frequency transcutaneous electrical nerve stimulation attenuates postsurgical pain and inhibits excess substance P in rat dorsal root ganglion.
BACKGROUND
Transcutaneous electrical nerve stimulation (TENS) is a common therapeutic modality for pain management, but its effectiveness in skin/muscle incision and retraction (SMIR)-evoked pain is unknown. We aimed to examine the effects of TENS on postoperative pain and the levels of substance P (SP), N-methyl-D-aspartate receptor 1 (NR1), and interleukin 1β (IL-1β) in rat dorsal root ganglion (DRG).


METHODS
High-frequency (100 Hz) TENS was administered daily beginning on postoperative day 1 (POD1) and continued until animal subjects were killed for tissues. Mechanical sensitivity to von Frey stimuli (6g and 15g) and the levels of NR1, SP, and IL-1β in DRG were assessed in the sham-operated, SMIR-operated, TENS after SMIR surgery, and placebo-TENS after SMIR surgery groups.


RESULTS
Skin/muscle incision and retraction rats exhibited a significant hypersensitivity to von Frey stimuli on POD3. In contrast with SMIR rats, SMIR-operated rats receiving TENS therapy demonstrated a rapid recovery of mechanical hypersensitivity. The SMIR-operated rats showed an up-regulation of NR1, SP, and IL-1β in DRG on PODs 14 and 28, whereas the SMIR-operated rats after TENS administration reversed this up-regulation. By contrast, the placebo-TENS after SMIR operation did not alter postsurgical pain nor the levels of NR1, SP, and IL-1β.


CONCLUSIONS
Our data demonstrated that TENS intervention reduced persistent postoperative pain caused by SMIR operation. Up-regulation of NR1, SP, and IL-1β in DRG, activated after SMIR surgery, is important in the development of prolonged postincisional pain. The TENS pain relief may be related to the suppression of NR1, SP, and IL-1β in DRG of SMIR rats.
From the *Department of Physical Therapy, China Medical University, Taichung; †Department of Medical Research, Chi-Mei Medical Center; ‡Department of Food Sciences and Technology, Chia Nan University of Pharmacy and Science, Jen-Te; §Department of Anesthesiology, Chi-Mei Medical Center, Yong Kang; and ∥Institute and Department of Physical Therapy, National Cheng Kung University, Tainan City, Taiwan.
Yu-Wen
YW
Chen
Jann-Inn
JI
Tzeng
Min-Fei
MF
Lin
Ching-Hsia
CH
Hung
Pei-Ling
PL
Hsieh
Jhi-Joung
JJ
Wang
D000818:Animals; D005727:Ganglia, Spinal / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D008297:Male; D010147:Pain Measurement; D010149:Postoperative Pain / Q000628:therapy*; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*
D053583:Interleukin-1beta; D016194:Receptors, N-Methyl-D-Aspartate; D013373:Substance P