Electro-acupuncture attenuates behavioral hyperalgesia and selectively reduces spinal Fos protein expression in rats with persistent inflammation.

Complementary Medicine Program, University of Maryland School of Medicine, Baltimore, 21207, USA.

This study examined the effect of electro-acupuncture (EA) on persistent inflammatory hyperalgesia in a rat model. Inflammation and hyperalgesia were induced by injecting complete Freund's adjuvant (CFA) into one hindpaw of the rat. Hyperalgesia was determined by a decrease in paw withdrawal latencies (PWL) to a noxious thermal stimulus. EA was applied bilaterally at the acupuncture point Huantiao (G30) at the rat's hindlimbs. EA-treated rats (n = 11) had significantly longer PWLs as compared with placebo control rats (n = 7) in the inflamed paw at 2.5 hours and 5 days after injection of CFA (P <.05) and longer PWLs as compared to sham control rats (n = 9) at 2.5 hours (P >.05). Paw edema was significantly reduced in EA-treated rats versus placebo controls at 24 hours after inflammation (P <.01). Inflammation-induced spinal Fos expression in the medial half of laminae I-II in EA-treated rats versus placebo rats (n = 5 per group) was significantly reduced (P <.01). These data showed that EA delayed the onset and facilitated the recovery of inflammatory hyperalgesia and suppressed the inflammation-induced spinal Fos expression in neurons (laminae I-II) involved in receiving noxious stimulation. This rat model of persistent pain and inflammation seems to be an ideal animal model for studying the effect of acupuncture.

PMID: 14622832 [PubMed]