Study on activation mechanism of SGCs in representation along the distribution of stomach meridian in IBS-D mice

To explore the peripheral neural mechanism underlying representation along the distribution of stomach meridian induced by intestinal inflammatory reaction using diarrhea predominant-irritable bowel syndrome (IBS-D) mice.

Among 62 healthy male C57BL/6 mice of clean grade, 12 mice were randomly selected and divided into a control group and a model group, 6 mice in each group, additionally, 12 mice were randomly selected and divided into a Tianshu group, a Liangqiu group and a Zusanli group, 4 mice in each group. In the model group, citrobacter was administered orally to establish IBS-D model. In the control group and the model group, the visceral pain threshold was observed using fecal colorectal distension (fCRD) induced electromyography of external oblique muscle, the positive cell number of neutrophil in the colonic muscularis was detected by myeloperoxidase (MPO) staining, the number, location and distribution rule of Evans blue (EB) extravasation points were observed by injection of EB staining solution into the tail vein. In the Tianshu group, the Liangqiu group and the Zusanli group, fluorescent dye Dil was injected at bilateral "Tianshu" (ST25), "Liangqiu" (ST34) and "Zusanli" (ST36) respectively, to observe the dye-positive cell number in different dorsal root ganglion (DRG) segments. In the control group and the model group, the activation of satellite glial cells (SGCs) in different DRG segments was observed by immunofluorescence.

Compared with the control group, in the model group, the area under curve of electromyography of external oblique muscle was increased at fCRD of 25, 50 and 75 μL distilled water (P＜0.001, P＜0.01); the MPO-positive cell number of neutrophil in the colonic muscularis was increased (P＜0.01). Few EB extravasation points could be found in the control group, while there were much more EB extravasation points observed in the model group, which was specially distribution in the area of stomach meridian, from "Huaroumen" (ST24) to "Zusanli" (ST36), as well as the surface area dominated by L₂-L₅ segment of the spinal cord. The Dil-positive cells were mainly exhibited in the DRG of T₁₁, L₅ and L₄ segments in the Tianshu group, the Liangqiu group and the Zusanli group, respectively. Compared with the control group, the ratio of glial fibrillary acidic protein (GFAP)/glutamine synthetase (GS) co-expression was increased in the DRG of T₁₁, L₄ and L₅ segments in the model group (P＜0.05, P＜0.01).

The activation of SGCs within DRG of T₁₁, L₄ and L₅ segments may relate closely to the occurrence of the representation along the stomach meridian distribution in IBS-D mice.