To explore the effects of Modified Sijunzi Decoction (四君子汤加减) on 5-hydroxytryptamine (5-HT) receptor, serum inflammation and brain-gut peptide in patients with irritable bowel syndrome (IBS).

A total of 122 IBS patients were randomly divided into Sijunzi Decoction group and control group (61 cases in each group). Both groups were treated with western medicine, and the Sijunzi Decoction group was treated with Modified Sijunzi Decoction on the basis of western medicine and the treatment time was 28 d. The changes of TCM syndrome integral, 5-HT receptor mRNA of intestinal mucosa, serum inflammation and brain-gut peptide were observed.

There was no statistically significant difference in traditional Chinese medicine syndrome scores between the two groups before treatment (P>0.05). After treatment, both groups had a decrease in scores (P<0.05), and the score of the Sijunzi Decoction group was lower than that of the control group (P<0.05). There was no statistically significant difference in the expression levels of 5-HT receptors between the two groups before treatment (P>0.05). After a period of treatment, both groups showed a decrease (P<0.05), and level of the Sijunzi Decoction group was lower than that of the control group (P<0.05). There was no statistically significant difference in serum inflammatory cytokine levels between the two groups before treatment (P>0.05). The serum levels of interleukin (IL)-8, IL-10, IL-12 and tumor necrosis factor-α (TNF-α) all decreased after treatment (P<0.05), and the levels of the Sijunzi Decoction group were lower than those of the control group (P<0.05), while IL-10 was higher than before treatment (P<0.05), and the level of the Sijunzi Decoction group was higher than that of the control group (P<0.05). There was no statistically significant difference in brain gut peptide levels between the two groups before treatment (P>0.05). After treatment, the levels of vasoactine intrestinal peptide (VIP), calcitonin gene-related peptide (CGRP) and 5-HT in both groups decreased compared to those before treatment (P<0.05), and the levels of the Sijunzi Decoction group was lower than those of the control group (P<0.05). Neuropeptide Y (NPY) levels all increased (P<0.05), and the level of the Sijunzi Decoction group was higher than that of the control group (P<0.05). The total effective rates of the Sijunzi Decoction group and the control group were 91.80% (56/61) and 75.41% (46/61), respectively, with statistical differences (P<0.05) between the two groups.

Sijunzi Decoction can significantly improve the clinical symptoms and improve the efficacy of IBS. The mechanism may be related to regulating the expression of 5-HT receptor in intestinal mucosa, improving the level of brain-intestinal peptide, and inhibiting inflammatory response.