Autonomically mediated anti-inflammatory effects of electrical stimulation at acupoints in a rodent model of colonic inflammation

Background Acupuncture has been widely accepted for treatments of many diseases. This study was performed to determine effects and mechanisms of electroacupuncture (EA) by chronically implanted electrodes at acupoint ST36 on colonic inflammation induced by TNBS in rats. Methods After intrarectal administration of TNBS, the rats were treated with sham-EA, EA1/EA2 (two sets of parameters) for 3 weeks. Disease activity index (DAI), macroscopic and microscopic lesions, plasma levels of TNF-alpha, IL-1 beta and IL-6 were observed as evaluation of inflammatory responses. The autonomic function was assessed by analysis of the heart rate variability. Results (a) Vagal activity was significantly increased with both acute and chronic EA1/EA2; (b) DAI was significantly decreased with both chronic EA1 and EA2, and EA2 was more potent than EA1 (P < 0.05); (c) The macroscopic score was 6.4 +/- 0.6 with sham-EA and reduced to 4.9 +/- 0.1 with EA1 (P < 0.05) and 4.0 +/- 0.2 with EA2 (all P < 0.05). The histological score was 4.05 +/- 0.58 with sham-EA and remained unchanged (3.71 +/- 0.28) with EA1 (P > 0.05) but reduced to 3.0 +/- 0.3 with EA2 (P < 0.01); (d) The plasma levels of TNF-alpha, IL-1 beta and IL-6 were significantly decreased with EA2. Conclusions Electrical stimulation at ST36 improves colonic inflammation in TNBS-treated rats by inhibiting pro-inflammatory cytokines via the autonomic mechanism.