[Electroacupuncture of "Tianshu" (ST25) alleviates ulcerative colitis by activating sacral parasympathetic postganglionic neurons of the pelvic ganglion in mice].

Objectives: To observe the effect of electroacupuncture (EA) of bilateral "Tianshu" (ST25) on ulcerative colitis (UC) in mice, and further investigate its related neural circuits including colonic-associated sympathetic and sacral parasympathetic postganglionic components.

Methods: Thirty C57BL/6J male mice were randomly divided into normal control, model and EA groups, with 10 mice in each group. The UC model was established by free access to 3% dextran sulfate sodium (DSS) solution for 7 consecutive days. Under isoflurane inhalation anesthesia on day 1, 3, 5, and 7 of modeling, mice of the EA group received EA stimulation of bilateral ST25 (2 mA, 10 Hz) for 30 min each time. The colonic histopathological changes were assessed by HE staining, and the body weight of mice was recorded. The relative abundance values of acetylcholine (ACh) and norepinephrine (NE) in the distal colon tissues were detected by using high performance liquid chromatography-mass spectrometry. In addition, six male C57BL/6J mice were randomly and equally divided into model and EA groups. On the fifth day of modeling, mice in the EA group received once EA stimulation with the same operations above, while mice in the model group were only anesthestized without EA. Immunofluorescence staining was used to examine the expression of c-Fos protein of the tyrosine hydroxylase-positive (TH⁺) neurons in the superior mesenteric ganglion (SMG), inferior mesenteric ganglion (IMG), and vesicular acetylcholine transporter-positive (VAChT⁺) neurons in the pelvic ganglion (PG).

Results: From day 7 to 9 of DSS modeling, the model group showed significant decrease of body weight compared to the normal control group (P<0.001), and the EA group showed a significantly lower reduction in body weight in contrast to the model group (P<0.01, P<0.05). The histopathological score (thickening of the colon wall, injury of the lamina propria structure, submucosal edema, and inflammatory cell infiltration) was significantly increased after modeling (P<0.000 1) and obviously improved after EA (P<0.001). Compared with the normal group, the relative abundance of ACh in the distal colon of the model group decreased significantly (P<0.05), which increased significantly in the EA group (P<0.05) when compared with the model group. No significant differences were found among the 3 groups in the relative abundance value of NE in the distal colonic tissues. Results of immunofluorescence staining showed that, compared with the model group, there were no statistically significant differences in the expression of c-Fos in TH⁺ neurons of SMG and IMG (sympathetic postganglionic component innervating the colon tissue) in the EA group. However, compared with the model group, the number of VAChT⁺ neurons that express c-Fos in PG of the EA group increased significantly (P<0.05).

Conclusions: EA of bilateral ST25 can ameliorate the inflammatory response and histopathological injury in UC mice, which may be achieved by activating the sacral parasympathetic postganglionic neurons in the PG instead of sympathetic postganglionic components.