The antidepressant potential of lactobacillus casei in the postpartum depression rat model mediated by the microbiota-gut-brain axis

Lactobacillus casei, a kind of probiotic, was reported as antidepressant effects. However, little is known about the effect of Lactobacillus casei on postpartum depression (PPD). In this study, we investigated the effects of Lactobacillus casei in improving PPD and potential mechanisms. Four hours of daily maternal separation from postnatal day 2 to day 21 was performed to establish the PPD model in rats. From postnatal day 2 to day 28, rats were gavage-fed with an equal volume of normal saline, Lactobacillus casei (8 × 108 CFU/kg/day), or paroxetine (1.8 mg/kg/day), respectively. Rat behaviors were measured using the sucrose preference test, the elevated plus maze, the forced swim test, and the tail suspension test. Changes in gut microbiota were detected by real-time fluorescence quantitative PCR. Administration of Lactobacillus casei improved depressive-like behaviors, intestinal microflora, and oxidative stress in PPD model rats. Western Blot or HPLC assays showed that Lactobacillus casei intervention reversed the changes of brain-derived neurotrophic factor (BDNF), N-methyl-D-aspartic acid receptor 1 (NR1), ERK1/2, and monoamines in the brain of PPD rats. These results suggest that Lactobacillus casei could improve PPD through altering gut microbiota composition, brain monoamines and oxidative stress, which may be associated with the regulation of the BDNF-ERK1/2 pathway.