Antidepressant-like activity of Chaihu-Shugan-San aqueous extract in rats and its possible mechanism

Background: Chaihu-Shugan-San (CHSGS), a traditional Chinese medicinal formula, is commonly used for the treatment of depression in China. However, the molecular mechanism underlying its antidepressant action is unknown. Objective: The objective of this study is to evaluate the antidepressant-like effects of CHSGS and further explore the possible molecular mechanism implicated in its actions. Materials and Methods: The rats were randomly divided into four groups: The normal control group, the model control group, the CHSGS group and the fluoxetine control group. The antidepressant-like effects of CHSGS aqueous extract were assessed in rats exposed to chronic mild stress (CMS) using the open-field test and sucrose water consumption test, its underlying mechanism of anti-depression was explored by determining the effect of CHSGS on the extracellular signal-regulated kinase (ERK) and phospho-ERK (P-ERK) in the hippocampus using western blot. The aqueous extract of CHSGS at a dose of standard (5.9 g/kg.d) was administered intragastrically for 14 days during the CMS model while the fluoxetine control group was given at the same time using fluoxetine hydrochloride (1.8 mg/kg.d). Results: The stressed rats demonstrated decreased locomotor activity in open field test and reduction in sucrose consumption and decreased levels of P-ERK1/2 and the ratio of P-ERK1/2 to total ERK1/2 in the hippocampus. CHSGS alleviated the depressive-like behaviors and increased levels of P-ERK1/2 and the ratio of P-ERK1/2 to total ERK1/2 in stressed rats as well as fluoxetine. Conclusion: In summary, these results suggest that CHSGS aqueous extract possesses an antidepressant-like activity in CMS induced depression model rats, which might be mediated, at least in part, by reversing the stress-induced disruption of ERK activity.