Objective: To observe the effects of acupuncture plus medication therapy on behavior

intestinal flora

and the expression of 5-hydroxytryptamine (5-HT) and 5-hydroxytryptophan (5-HTP) in depressed rats

and to explore the possible mechanism of acupuncture plus medication in the treatment of depression. Methods: Thirty-five male SD rats were randomly divided into a blank group

a model group

an electroacupuncture (EA) group

a fluoxetine group

and an acupuncture plus medication group

with 7 rats in each group. The depressed rat model was prepared by exposing to chronic unpredictable mild stress (CUMS). In the EA group and the acupuncture plus medication group

the rats were intervened by EA at "Yaoyangguan"

bilateral "Tianshu"

"Zusanli"

and "Changshu"

30 minutes each time

once a day for 21 days. In the fluoxetine group and the acupuncture plus medication group

the rats received intragastric administration with 0.2% fluoxetine at 10 mg/kg

once a day for 21 days. The sucrose preference test (SPT)

open field test (OFT)

and forced swimming test (FST) were performed to analyze the behavioral changes of rats. The diversity of intestinal flora was detected by 16S rDNA high-throughput sequencing. The levels of 5-HT in hippocampus

colon

and serum

and 5-HTP in colon and serum were detected by enzyme-linked immunosorbent assay (ELISA). Results: Compared with the blank group

in the model group

the sugar water consumption of SPT and the total distance of OPT were significantly decreased

the immobility time of FST was significantly increased

the levels of 5-HT in hippocampus

5-HT and 5-HTP in colon tissue and serum were significantly decreased (P<0.01)

and the species and relative abundance of intestinal beneficial flora were decreased. Compared with the model group

in each intervention groups

the sugar water consumption of SPT and the total distance of OPT were significantly increased

the immobility time of FST was significantly decreased

the levels of 5-HT in hippocampus

5-HT and 5-HTP in colon tissue and serum were increased (P<0.01

P<0.05)

and the species and relative abundance of intestinal beneficial flora were increased. Compared with the fluoxetine group

in the acupuncture plus medication

the immobility time of FST was decreased

the levels of 5-HT in hippocampus and serum were increased (P<0.05)

and the increasing trend of beneficial flora and the decreasing trend of harmful flora was more obvious. Conclusion: Acupuncture plus fluoxetine therapy could significantly alleviate the depression-like behavior in CUMS rats. And its mechanism may be related to the increasing the species and relative abundance of intestinal beneficial flora and up-regulating the expression of brain-gut axis 5-HT

5-HTP and other related molecules.