AUTHOR=Meng Yangyang , Feng Ya , Hang Lu , Zhou Yan , Wang Enkang , Yuan Jianye 

TITLE=No synergistic effect of fecal microbiota transplantation and shugan decoction in water avoidance stress-induced IBS-D rat model

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.995567

DOI=10.3389/fmicb.2022.995567

ISSN=1664-302X

ABSTRACT=Background:
The metabolism of 5-hydroxytryptamine (5-HT, serotonin) is involved in the pathogenesis of Irritable bowel syndrome (IBS). Shugan decoction (SGD) and fecal microbiota transplantation (FMT) can alleviate the symptoms of IBS. 
Aim:
The main purpose of this study is to confirm the effect of fecal microbiota liquid (FML) derived from healthy rats on IBS-like symptoms induced by WAS and to observe the synergistic effect of this fecal microbiota transplantation (FMT) with SGD. Moreover, 5-HT signal related mechanisms of action of FMT and the possible material basis of the FML were investigated.
Methods: 
The number of fecal pellets output (FPT) in 1 hour and the pain pressure threshold (PPT) in each group were recorded; the histological changes of colon mucosa were observed; and the number of enterochromaffin cells (ECs), the content of 5-HT and the expression of serotonin reuptake transporter (SERT) protein in colon were detected by immunofluorescence or western blotting.
Results:
Compared with that in Control, the PPT and the expression of SERT in WAS→Control was decreased accompanied with the increased number of ECs and the level of 5-HT in colon, but the FPT was not increased although that was increased in the WAS. Compared with that in WAS, the FPT, the PPT, the number of ECs, the level of 5-HT and the expression of SERT protein in colon in SGD, control→WAS, SGD→WAS and SGD+(Control→WAS) were all restored. Compared with that in WAS, the FPT, the PPT, the number of ECs, the level of 5-HT and the expression of SERT protein in colon in Control→WAS and FControl→WAS were restored. There were no significant difference between Control→WAS and FControl→WAS.
Conclusions:
The FML derived from WAS rats is able to cause partial IBS-like symptoms in normal rats and SGD or the FML derived from normal rats can either effectively alleviate the IBS symptoms induced by WAS without synergistic effect maybe by restoring intestinal microbial homeostasis and reducing the level of 5-HT in colon. The metabolites of intestinal microflora in the FML derived from normal rats maybe play an important role as the mainly effective substances.