Objective: To investigate the antidepressant-like effects of Chaihu Shugan Powder (CSP, ) and to explore its underlying mechanisms.
Methods: Thirty-two Sprague-Dawley rats were randomly divided into control (CON), chronic unpredictable mild stress (CUMS), fluoxetine (FLU), and CSP groups, 8 rats in each group. All of the rats except for those in the control group were subjected to 3 consecutive weeks of CUMS to establish the depression model. The open field test (OFT), forced swimming test (FST), and sucrose preference test were used to assess the anti-anxiety and antidepressant effects of CSP. Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling was used to determine the apoptosis rate in the hippocampal tissues. The mRNA and protein levels of glucose-regulated protein (GRP) 78, spliced X-box-binding protein (XBP)-1, CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, and c-Jun N-terminal kinase (JNK) in the hippocampus of rats were evaluated by real-time PCR and Western blot analysis, respectively.
Results: Administration of CSP alleviated anxiety and depression-like behavior in CUMS rats, as revealed by enhanced time and distance in the center of the OFT (P<0.05), an increased preference for sucrose, and longer swimming time and shorter immobility time during the FST (all P<0.05). In addition, CSP treatment significantly reduced the rate of apoptosis in rat hippocampal neurons (P<0.05). The mRNA and protein expression levels of GRP78, spliced XBP-1, and CHOP were down-regulated along with the expression of caspase-12 and cleaved caspase-12 proteins (all P<0.05), whereas total and phosphorylated JNK1 protein levels did not differ significantly between control and CSP-treated rats.
Conclusion: CSP can improve depression-like behavior in rats exposed to CUMS, possibly by suppressing CHOP and caspase-12 mediated apoptosis in the rat hippocampus.
Keywords: Chaihu Shugan Powder; Chinese medicine; apoptosis; chronic unpredictable mild stress; depression; endoplasmic reticulum stress.