Mechanism of Electroacupuncture on Postoperative Ileus Induced by Surgical Stress in Rats

Abstract

Objectives: Acupuncture has been used for treating gastrointestinal (GI) disorders such as postoperative nausea and vomiting. Electroacupuncture (EA) accelerates GI transit following surgery and ameliorates postoperative ileus (POI) to restore colonic transit (CT); however, the mechanisms of this EA-induced restoration remain unclear. The aims of this study were to show CT following surgery and the effects of EA at ST 36 on POI induced by surgical stress (SS) in 45 conscious, male Sprague-Dawley rats. Materials and Methods: An operation was performed in each rat, setting a cannula into the cecum to connect the proximal colon to inject markers. On the day after surgery, 20 metal radiopaque markers were administered to the proximal colon of each rat. These markers were visible throughout the GI tract on soft X-ray immediately after administration and up to 240 minutes afterward. The rats were divided into 5 groups with 9 rats in each group: (1) SS; (2) 5 days post surgery (POST-5D); (3) SS + phentolamine; (4) EA alone; and (5) EA + atropine. The EA was performed at ST 36 for 20 minutes at a frequency of 10 Hz and agents were administered in the appropriate groups before markers were administered and measurements were taken. Measurements were performed the day after surgery except in the POST 5-D group. CT was calculated by the geometric center on the images showing the CT for each rat. Results: CT after surgery was delayed significantly and phentolamine accelerated CT. EA restored CT following surgery and atropine abolished the effect of EA on CT. Conclusions: The current study demonstrated that surgery induced a delay in CT through the sympathetic pathway via α-adrenoreceptors; CT was restored by EA. These results suggest that EA can be used to treat POI through mediation of the autonomic nervous system.

Keywords: autonomic nervous system; colonic transit; electroacupuncture; postoperative ileus.

FIG. 1.

Imaging of each groups' colonic transit of radiopaque markers. Scale bar = 50 mm. The markers were colored differently for each time point. (A) Surgical stress (SS) group. (B) Five days after surgery [POST-5D] group. (C) SS + PA [phentolamine] group. (D) EA [electroacupuncture] alone group. (E) EA + A [atropine] group. Color images are available online.