Abstract: “Psychobiotics” are a class of probiotics that have regulatory effects on neurobehavioral functions. With the maturity of the “microbiota-gut-brain axis” theory, psychobiotics have been widely used in the prevention and treatment of psychiatric diseases. In this study, mice under the chronic unpredictable mild stimulus (CUMS) were treated with multiple probiotics (Bifidobacterium breve CCFM1025, Bifidobacterium infantis CCFM687, and Pediococcus lactis CCFM6432) for four weeks. Multiple probiotics intervention improved the sucrose preference, reduced the immobile time in forced swim test, and increased the activity in open arms of elevated plus maze of the chronically stressed mice. The mechanism of action correlated with the down-regulation of serum corticosterone and pro-inflammatory cytokines (TNF-α and IL-1β) in the prefrontal cortex. Chronically stressed mice also showed significant constipation symptoms. Probiotics treatment increased the defecation speed which was possibly through the elevation of cecum short-chain fatty acids, 5-hydroxytryptamine (5-HT) and Htr4 gene expression. Besides, significantly positive correlations were observed between the intestinal L-tryptophan (L-Trp) and brain L-Trp/5-HT levels in the mice treated with probiotics, which indicates that the regulation of intestinal and brain L-Trp/5-HT synthesis may contribute to both constipation and depression. This study confirms the psychobiotic potential of the multiple probiotics, expands the application of probiotics, and provides novel insight for the treatment of depression and accompanied constipation.
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