Effect of Lactobacillus casei on the depressive behavior and the expression of NR1 and NR2A receptors in hippocampus of rats with postpartum depression induced by maternal separation

Abstract

Objective To investigate the effect of Lactobacillus casei on depressive behavior and the expression of NR1, NR2A receptor in postpartum depression rats induced by maternal separation. Methods Twenty-four Sprague-Dawley female rats were randomly divided into control group(CON group) (n=8), postpartum depression group(PPD group) (n=8), postpartum depression with lactobacillus casei group(PPD+ Lactobacillus casei group) (n=8). Rats of the control group were given no interventions.Rats in PPD group and PPD+ Lactobacillus casei group were given maternal separation to establish depression model.And then the rats in PPD+ Lactobacillus casei group were treated with Lactobacillus casei(8×108CFU/(kg·d)) for 4 weeks after 14 days of maternal separation.The forced swimming test (FST) was employed to detect the depressive behaviors.Lactobacillus, Bifidobacterium, Enterococcus faecalis and Escherichia coli in cecum of rats and the expression of NR1 and NR2A mRNA in hippocampus of rats were detected by real-time fluorescence quantitative PCR. Results Compared with CON group ((157.50±8.13) s), the immobility time of PPD group((200.00±10.35) s) was significantly longer (t=-3.23, P<0.05). Compared with PPD group, the immobility time of PPD+ Lactobacillus casei group ((153.25±7.41) s) was significantly shortened (t=3.67, P<0.05), and the depressive behavior was improved.Compared with CON group, the mRNA expression of Lactobacillus ((1.47±0.08), t=-5.87, P<0.01), Enterococcus faecalis ((1.23±0.08), t=-2.85, P<0.05) and Escherichia coli( (1.33±0.07), t=-4.96, P<0.01) in caecum were significantly increased in PPD group, while that of Bifidobacterium decreased significantly((0.65±0.07), t=5.18, P<0.01). Compared with PPD group, the mRNA expression of Lactobacillus( (1.05±0.05), t=3.67, P<0.01), Enterococcus faecalis ((0.97±0.05), t=2.74, P<0.05) and Escherichia coli ((1.06±0.05), t=3.31, P<0.01) were significantly decreased in PPD+ Lactobacillus casei group, while that of Bifidobacterium increased significantly ((0.98±0.04), t=-4.26, P<0.01). Compared with CON group, the mRNA expression of NR1 receptor ((0.57±0.04), t=9.65, P<0.01) and NR2A receptor ((0.60±0.05), t=8.64, P<0.05) in hippocampus of rats in PPD group were significantly decreased.Compared with PPD group, the expression of NR1 receptor ((1.01±0.05), t=-5.39, P<0.01) and NR2A receptor ((0.98±0.07), t=-3.91, P<0.05) in hippocampus were increased significantly in PPD+ Lactobacillus casei group. Conclusion Lactobacillus casei can improve the depressive behavior of postpartum depression in rats, and improve the intestinal flora, which affect the expression of NR1 and NR2A in hippocampus. Key words: Postpartum depression; Hippocampus; Intestinal flora; Lactobacillus casei; NR1 receptor; NR2A receptor; Rat