Objective: To investigate the effect of acupuncture intervention on the depression behavior and expression of extracellular signal-regulated protein kinases (ERK 1/2), p-ERK 1/2 and brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of chronic unpredictable mild stress (CUMS) induced depression rats, so as to explore its antidepressant mechanism.
Methods: Sixty-four male SD rats were randomly divided into control, model, acupuncture, Fluoxetine, model ＋ Dimethyl sulfoxide (DMSO), model ＋ PD 98059(an ERK pathway inhibitor), acupuncture ＋ PD 98059 and Fluoxetine ＋ PD 98059 groups (n＝8 rats in each). The CUMS depression model was established by using chronic mild and unpredictable stress methods for 21 days. Manual acupuncture stimulation was applied to "Baihui" (GV 20) and "Yintang" (GV 29) for 10 min before modeling, once daily for 21 days. Fluoxetine hydrochloride suspension (1.8 mg•kg－1•d－1) was given to rats of the Fluoxetine group and Fluo-xetine ＋ PD 98059 group by gavage 30 min before CUMS. PD 98059 (dissolved in DMSO, 10 µL) was administered to rats of model ＋ PD 98059 group, acupuncture ＋ PD 98059 and Fluoxetine ＋ PD 98059 group, and DMSO (10 µL) to rats of model ＋ DMSO group by intracerebroventricular injection 1 h before CUMS. Sucrose consumption test was carried out to evaluate the depressive behavior. Western blot was performed to detect the expression of ERK 1/2, p-ERK 1/2 and BDNF of prefrontal cortex.
Results: Compared with the control group, the sucrose consumption and the expression levels of p-ERK 1/2 and BDNF protein in the prefrontal cortex were significantly reduced in the model and model＋DMSO group (P<0. 01). After the intervention, modeling induced decrease of the sucrose consumption, and p-ERK 1/2 and BDNF expression was significantly up-regulated in both acupuncture and Fluoxetine groups (P<0.01, P<0.05), but not in the model＋PD 98059, Fluoxetine ＋PD 98059 and acupuncture＋PD 98059 groups (P>0.05). No significant differences were found among the model＋PD 98059, Fluoxetine ＋PD 98059 and acupuncture＋PD 98059 groups in the sucrose consumption, and ERK 1/2, p-ERK 1/2 and BDNF expression levels (P>0.05), and in the expression levels of ERK 1/2 protein among the 8 groups (P>0.05).
Conclusion: Acupuncture intervention has an anti-depressive role in CUMS induced depression rats, which may be related to its effects in up-regulating the expression of p-ERK 1/2 and BDNF in the prefrontal cortex tissue.
Keywords: Acupuncture; Brain-derived neurotrophic factor; Chronic unpredictable mild stress; Depression; Extracellular regulated protein kinases; PD 98059.