Objective:To determine the mechanisms underlying the anti-depressant effects of Kaixin Jieyu Decoction(开心解郁汤,KJD)by investigating the effects of KJD on behavior,monoamine neurotransmitter levels,and serotonin(5-HT)receptor subtype expression in the brain in a rat model of depression.Methods:The rat depression model was established using chronic unpredictable mild stress(CUMS).Forty-eight Sprague Dawley rats were randomly divided into control,depression model(CUMS),CUMS±KJD(7.7 g/kg~(-1)·d~(-1)of crude drug),and CUMS+fluoxetine(2.4 mg/kg~(-1)·d~(-1))groups(n=12 in each group),and the treatments lasted for 21 days.We regularly evaluated body weight,sucrose consumption,and horizontal and vertical activity scores in open-field tests.The content of the monoamine neurotransmitters 5-HT,norepinephrine(NE),and dopamine(DA)and the DA metabolite homovanillic acid in the cerebral cortex,and 5-HT_(1A)and 5-HT_(2A)receptor mRNA in the cerebral cortex and the hippocampus,were determined respectively by high-performance liquid chromatography-coularray electrochemical detector and real-time polymerase chain reaction.Results:Compared with the control group,CUMS rats showed a variety of depression-like behavioral changes,including a significant reduction in body weight,sucrose consumption,and horizontal and vertical activity scores in open-field tests(P<0.05 or P<0.01),and a significant decrease in 5-HT and NE levels and 5-HT_(2A)receptor mRNA expression.In contrast,they showed a significant increase in 5-HT_(1A)receptor mRNA expression in the cerebral cortex.In the hippocampus,5-HT_(1A)receptor mRNA expression was lower whereas 5-HT_(2A)receptor mRNA expression was higher than in the control group(P<0.05 or P<0.01).Treatment with KJD or fluoxetine partially attenuated these changes(P<0.05 or P<0.01).Conclusion:KJD could normalize the levels of 5-HT and NE and adjust the balance of 5-HT_(1A)and 5-HT_(2A)receptor expression in rat cerebrum,and this may be one of mechanisms of antidepressant effects of KJD. Objective: To determine the mechanisms underlying the anti-depressant effects of Kaixin Jieyu Decoction by investigating the effects of KJD on behavior, monoamine neurotransmitter levels, and serotonin (5-HT) receptor subtype expression in the brain in a rat model of depression. Methods: The rat depression model was established using chronic unpredictable mild stress (CUMS) .Forty-eight Sprague Dawley rats were differentiated into control, depression model (CUMS), CUMS ± KJD (7.7 g / kg ~ (-1) · d -1 of crude drug, and CUMS + fluoxetine (2.4 mg / kg -1 d -1) groups (n = 12 in each group), and the treatments are lasted for 21 days. We generally recommend body weight, sucrose consumption, and horizontal and vertical activity scores in open-field tests. The content of the monoamine neurotransmitters 5-HT, norepinephrine (NE), and dopamine DA metabolite homovanillic acid in the cerebral cortex, and 5-HT_ (1A) and 5-HT_ (2A) receptor mRNA in the cerebral cortex and the hippocampus, were determined respectively by high-performance liquid chromatography-coularray electrochemical detector and real-time polymerase chain reaction. Results: Compared with the control group, CUMS rats showed a variety of depression-like behavioral changes, including a significant reduction in body weight, sucrose consumption, and horizontal and vertical activity scores in open-field tests (P <0.05 or P <0.01), and a significant decrease in 5-HT and NE levels and 5-HT 2A receptor mRNA expression. contrast, they showed a significant (1A) receptor mRNA expression in the cerebral cortex. the hippocampus, 5-HT (1A) receptor mRNA expression was lower than that in the control group (P <0.05 or P <0.01). Treatment with KJD or fluoxetine partially attenuated these changes (P <0.05 or P <0.01) .Conclusion: KJD could normalize the levels of 5-HT and NE and adjust the balance of 5-HT - (1A ) and 5-HT 2A receptor expression in rat cerebrum, and this may be one of the mechanisms s of antidepressant effects of KJD.