Abstract: ObjectiveTo investigate the mechanism of attenuating effect of physical exercise on chronic stress-induced hippocampal damages through observing different effects of exercise and stress on 5-HT level and the mRNA expression level of 5-HT_1A receptor(5-HT_1A R).Methods24 adult male Wistar rats were randomly divided into four groups as follows:control group,exercise group,chronic stress group,exercise plus chronic stress group and 5-HT levels were detected by high-performance liquid chromatography using electrochemical detection,and the expression levels of 5-HT_1A R mRNA were measured by real-time fluorescence quantitative reverse transcription polymerase chain reaction(R T-FQ-PCR).ResultsCompared with the control group,5-HT levels in hippocampus increased significantly in the exercise group(P< 0101),decreased significantly in the chronic stress group(P<0.01).Compared with the chronic stress group,5-HT levels were slightly higher than exercise stress group without statistecal significance(P>0.05).The relative expression levels of 5-HT_1AR mRNA in the exercise group and the chronic stress group are 4.49±1.59 and 0.22±0.06 times of those of the control group respectively with significant differences(P<0.01).The relative expression levels of 5-HT_1A R mRNA in the exercise stress group are 0.87±1.22 times of those of the control group,significantly higher than those of the chronic stress group(P<0.05).ConclusionExercise attenuates chronic stress-induced hippocampal damages through improving the function of 5-HT system in hippocampus.The up-expression of the 5-HT_1AR in hippocampus probably played a more important role.