Effect of probiotic administration on gut microbiota and depressive behaviors in mice

Background The gut microbiota is closely associated with the bidirectional gut-brain axis that modulates neuropsychological functions of the central nervous system, thereby affecting mental disorders such as depression. Although it is known that probiotics affect brain functions, the impact of probiotics on the regulation of the prevalence and composition of gut microbiota, leading to anti-depressive effects has not been well understood. Methods Mice were randomly divided into four different groups ( n = 10 for each group) as follows: Group G1 (normal group) as control and group G2 (stress group) were given sterile saline via oral route daily for 8 weeks without and with stress condition, respectively. Under the stress condition, group G3 (fluoxetine group) was administered with fluoxetine hydrochloride and group G4 (probiotic group) was orally given multi-strains of probiotics daily for 8 weeks. After treatment, all mice underwent behavioral testing. Furthermore, fecal samples were collected from randomly selected 5 mice of each group on day 60 and taxonomical analysis of intestinal microbial distribution was performed. Results Mice subjected to restraint stress showed depressive-like behaviors along with high corticosterone levels in serum. However, probiotic administration alleviated depressive-like behaviors and decreased corticosterone level. Moreover, fecal microbiota was distinctly altered in probiotic-treated mice of the stress group. The relative abundance of phylum and genus levels was significantly decreased in the stress group, but probiotic administration restored the composition of microbes restored. Conclusion Ingested probiotics alter the composition of gut microbiota, likely improving the symptoms of depression. Graphical abstract Probiotic administration alters gut microbiota and reduces depressive-like behaviors