Objective: To investigate the effect of subanesthetic dose of ketamine on gut microbiota among male and female depressed mice. Methods: The study included in 20 healthy male SPF mice and 20 female C57BL/6 mice

and they were randomly assigned to eight groups (n=5): female control group (FC group)

female control with ketamine treatment group (FCK group)

female depression group (FD group)

female depression with ketamine treatment group (FDK group)

male control group (MC group)

male control with ketamine treatment group (MCK group)

male depression group (MD group) and male depression with ketamine treatment group (MDK group). The ketamine (10 mg/kg) or saline (0.9% NaCl) were administrated by intravenation in each group. FD group

FDK group

MD group and MDK group were modeled by the chronic unpredictable mild stress (CUMS). The behavioral tests included force swimming test

sucrose preference test and open filed test. The gut microbiota of mice was detected by 16S rDNA amplicon sequencing. Qualitative analysis of bacteria in the specimen and predictive analysis of 16S rDNA function genes were conducted. The results were reported as mean values with their standard errors

and submitted to one-way ANOVA regardless sex difference and two-way ANOVA to analyze the effect of sex and ketamine on ameliorate depressive-like behaviors in mice

followed by the Tukey multiple comparisons test

with a statistical significance (P<0.05). Results: Compared with control group

the scores of forced swimming test were significantly prolonged

the scores of the sucrose preference test was significantly decreased

and the scores of open field test were significantly decreased (all P<0.05). These results were significantly ameliorated to varying degrees after subanesthetic dose of ketamine treatment (P<0.05). The diversity and abundance of intestinal flora in each group did not change significantly after CUMS and ketamine treatment. The reduction of Actinobacteria could be improved by subanesthetic dose of ketamine in depressed mice

regardless of sex difference. Furthermore

the relative abundance of Bacteroidaceae could be alleviated in depressed female mice

and Alistipes increased in depressed male mice. Conclusion: Mice of different genders showed different changes of intestinal flora in response to CUMS stimulation and subanesthetic ketamine treatment. The depressive-like behaviors can be ameliorated through increasing the abundance of Actinobacteria

alleviating the abundance of Bacteroidaceae in depressed female mice

and increasing Alistipes in depressed male mice after ketamine treatment.