Effect of electroacupuncture on 5-HT7R in gastric antrum and colon tissues of functional diarrhea rats

Abstract

To observe the effect of electroacupuncture(EA) at "Zusanli"(ST36), "Yinlingquan" (SP9) or "Yingu"(KI10) on the expression of 5-hydroxytryptamine type 7 receptor (5-HT7R) in the gastric antrum and colon tissues in functional diarrhea (FD) model rats, so as to explore its mechanisms underlying improving FD. Forty male SD rats were randomly divided into control, model, ST36, SP9 and KI10 groups，with 8 rats in each group. The FD model was established by combined administration of restriction (four-limbs' banding) + abdominal cold stimulation + feeding every other day, for 14 days. EA (2 Hz, 0.5 mA) was applied to bilateral ST36 or bilateral SP9 or bilateral KI10 in the 3 corresponding groups for 30 min, once a day for 7 days after successful modeling. Rats of the control group received restriction only. The fecal water content was calculated and the stool form score was given according to the Bristol's methods. The gastric residual rate (GRR) and small intestine propulsion rate (SIPR) were determined to assess the motility of the gastrointestinal tract. Immunohistochemical and real-time fluorescent quantitative PCR were used to detect the expression of 5-HT7R protein and mRNA of the gastric antrum and colon tissues, respectively. Compared with the control group, the fecal water content, the stool form score, the SIPR and the expression levels of 5-HT7R protein and 5-HT7R mRNA were significantly increased (P<0.01,P<0.05) and the GRR was considerably decreased in the model group (P<0.01). The fecal water content, stool form score and SIPR, and expression level of 5-HT7R protein and mRNA in the gastric antrum and colon were significantly lower in both the ST36 and SP9 groups (not in the KI10 group) than in the model group (P<0.01, P<0.05), but the GRR was significantly higher in the ST36 and SP9 groups (not in the KI10 group) than in the model group (P<0.01). The effects of both ST36 and SP9 were significantly superior to those of KI10 in improving all the indexes mentioned above （except SIPR and the mRNA level of 5-HT7R in the colon in SP9 group）(P<0.01, P<0.05). No significant differences were found between the ST36 and SP9 groups in lowering the levels of fecal water content, stool form score, SIPR, and the expression of 5-HT7R protein and mRNA, as well as in up-regulating GRR (P>0.05). EA of ST36 and SP9 can improve the motility of gastrointestinal tract in FD rats, which may be related to its functions in down-regulating the expression of 5-HT7R protein and mRNA in gastric antrum and colon tissues. The effects of ST36 and SP9 were obviously better than those of KI10 in ameliorating the gastric and intestinal motility (except GRR) and in lowering the expression of 5-HT7R protein and mRNA.