[Auricular electroacupuncture improves depression possibly by promoting hippocampal Raf/ERK/RSK/CREB signaling in chronic unpredictable mild stress induced depression rats].

OBJECTIVE: To observe the effect of auricular electroacupuncture (EA) on intracellular Raf/ extracellular signal-regulated kinase (ERK)/ ribosomal S6 kinase (RSK)/ cAMP response element-binding protein (CREB) signal pathway in the hippocampus of depression model rats, so as to explore its anti-depressive mechanism. METHODS: A total of 60 male SD rats were randomly divided into control, model, auricular EA, PD98059(ERK inhibitor), DMSO (Dimethylsulfoxide), PD98059+EA groups (n=10 in each group). The rats in the control group were fed with normal diet without any treatment. The depression model was induced by chronic unpredictable mild stress (CUMS) for consecutive 21 days. EA (20 Hz, 2 mA) was applied to bilateral auricular "Xin"(Heart) and "Shenmen" for 30 min, once daily for 28 days. Rats of the PD98059, DMSO and PD98059+EA groups received intracerebroventricular injection of PD98059(100 µmol/L), DMSO and PD98059 (dissolved by DMSO) solutions (5 µL/d), respectively, once daily for 28 days. Sucrose preference test (sucrose consumption) was conducted at the baseline, before and after the intervention. The expression of hippocampal Raf, phosphorylated (p)-Raf, ERK, p-ERK, RSK, CREB and p-CREB proteins were detected by Western blot after EA intervention. RESULTS: Following modeling, the sucrose consumption volume, and the expression levels of hippocampal Raf, p-Raf, ERK, p-ERK, RSK, CREB, p-CREB proteins were significantly lower in the model group than those in the control group (P<0.01). Following the treatment, the sucrose consumption and the expression levels of Raf, p-Raf, ERK, p-ERK, RSK, CREB, p-CREB in the auricular EA group and those of p-Raf, ERK and CREB in the PD98059+EA group were obviously increased in comparison with the model group (P<0.05, P<0.01), the expression level of p-ERK in the PD98059 group was obviously decreased in comparison with the model group (P<0.05), suggesting an improvement of depression after auricular EA. Compared with auricular EA group, the expression level of p-ERK, p-CREB and RSK in the PD98059+EA group were significantly decreased (P<0.05). CONCLUSION: EA of auricular "Xin" and "Shenmen" is able to improve depression in depression rats, which is probably related to its effect in promoting activities of hippocampal Raf/ERK/RSK/CREB signaling.