| Abstract |
【Abstract】Objective: Major depressive disorder(MDD) rat model was constructed by chronic unpredictable mild stress(CUMS). The levels of excitatory amino acid transporter 2(EAAT2) and glutamate in frontal lobe and the distribution of gut microbiota were detected, and to explore their relationship with the pathogenesis of MDD. Methods: Forty SD rats were randomly divided into control group, depression group (MDD group), Intervention group (Lac group and Flu group)，with 10 rats in each group. Control group were fed normally, and CUMS stimulation continued for 4 weeks in the other three groups. After successful modeling, CUMS stimulation continued in the MDD group, Lac group and Flu group were supplemented with lactobacillin tablets (0.12g/ml, 1.2g/kg, once a day) and fluoxetine administration (1mg/ml, 10mg/kg, Once a day) on the basis of CUMS for two weeks respectively.At the 4th and 6th week, the forced swimming experiment, open field experiment and water maze experiment were used to evaluate the behavior of the rats.After the 6th week, the content of glutamate in the prefrontal cortex of rats was detected by liquid mass spectrometry.The mRNA expression of eaat2 in the prefrontal cortex of rats was detected by qRT-PCR.The protein expression of EAAT2 in the prefrontal cortex of rats was detected by Western Blot. 16s rDNA sequencing was used to detect the difference of gut microbiota in each group.One-way ANOVA was used to compare behavior, glutamate and EAAT2 gene and protein levels in rats.Differential discriminant analysis was used to compare the composition of microflora among the groups. Results: After modeling, MDD group, Lac group and Flu group all showed expected depression-like behavior;After intervention, the rest time in Lac group and Flu group was significantly lower than that in MDD group, and the horizontal activity distance was significantly increased compared with MDD group (P<0.05). There was no statistical significance between the water maze groups (P>0.05).The dominant bacteria in the intestinal tracts of all groups changed. In the control group the dominant bacteria were actinomyces and bifidobacterium, in MDD group were Photobacterium and Selenomonadales, in Lac group were lactic acid bacteria, and in Flu group were Prevotella. Glutamate content in prefrontal cortex of MDD group was significantly higher than that of control group (P<0.05), Lac group and Flu group were significantly lower than that of MDD group (P<0.05);Compared with control group, eaat2 mRNA and protein levels in MDD group were significantly decreased (P<0.05), and eaat2 mRNA and protein levels in Lac and Flu groups were significantly increased compared with MDD group (P<0.05). Conclusion: The dominant bacteria in the gut of the four groups were different, and the contents of eaat2mRNA, EAAT2 protein and glutamate in the prefrontal cortex of MDD group, Lac group and Flu group were different.It is speculated that eaat2 mRNA, EAAT2 protein, glutamate level and gut micribiota may play an important role in the occurrence of depression-like behavior in CUMS rats.
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