Background Gut microbiota may affect brain function and stress response through the modulation of gut-brain axis (GBA). The relationship between gut microbiota and brain is particularly important for the growth and development of offspring.

Objective This experiment investigates the effect of chronic stress of pregnant rats on the gut microbiota of progeny, and preliminarily explores the improving effect of Lycium barbarum polysaccharide (LBP) on the emotional change of offspring caused by chronic stress during pregnancy and its possible mechanism.

Methods Twenty-four adult female SD rats were divided into a control group, a model group, and a model + LBP group; twenty adult male SD rats were divided into a control group and a model group. Chronic unpredictable mild stress (CUMS) was used to establish a rat model of chronic stress during pregnancy, and intragastric intervention was performed with LBP. The offspring rats were divided into a control offspring group, a model offspring group, and a model + LBP offspring group. The offspring's fresh stool samples were collected on postnatal day 20, the sequence of 16S rRNAV3-V4 regions of microorganisms in the feces of offspring was determined by Illumina MiSeq technique, and the interaction between microbial community structure and diversity were analyzed; their plasma corticosterone levels were detected by radioimmunoassay on postnatal day 28; their emotional changes were measured by open field test, sucrose preference test, and tail suspension test on postnatal day 42.

Results The plasma corticosterone levels of the female rats in the model group and the model + LBP group on the 7th and 14th days of stress were higher than that of the control group (P < 0.05), suggesting that the female rats were in stress during pregnancy. After the LBP intervention, the model + LBP offspring group showed higher body weight, horizontal movement score, and 1% sucrose preference percentage, and shorter resting time than the model group did(91.92±11.19) g vs. (81.06±15.71) g; (77.47±10.67) vs. (67.32±11.39); (67.00±6.00)% vs. (59.00±8.00)%; (113.39±16.75)s vs. (152.13±33.26)s (P < 0.05). The results of α diversity analysis showed that the Sobs index of the model + LBP offspring group (377.20±30.03) was higher than that of the model offspring group (311.00±11.87) (P < 0.05), and the Ace index of the model + LBP offspring group (409.38±16.06) was higher than the model offspring group (376.33±19.53) (P < 0.05). The relative abundance of Firmicutes phylum in the model+LBP offspring group was higher than that in the model offspring group, so was Lachnospiraceae family. The offspring's 1% sucrose preference percentage was positively associated with Enterobacteriaceae abundance (r=0.59) and Bacteroidaceae abundance (r=0.44), and negatively associated with Prevotella Shan and Collins abundance (r=-0.47); resting time was negatively associated with Streptococcus abundance (r=-0.51); horizontal movement score was negatively associated with Bifidobacterium abundance (r=-0.48) (P < 0.05).

Conclusion Chronic stress during pregnancy causes not only the mothers but also the offspring to be in a stress state. LBP can alleviate the maternal elevated stress level caused by chronic stress during pregnancy, positively affect the colonization of offspring's gut microbiota and the composition and diversity of microbial species, and improve the emotional changes of offspring caused by chronic stress during maternal pregnancy.