Objective: To observe the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on the motor function and the expression of glial fibrillary acidic protein (GFAP) and microtubule associated protein 2 (MAP2) in cerebral ischemic penumbra of rats with middle cerebral artery occlusion (MCAO) and explore the mechanism of taVNS in the improvement of motor function in MCAO rats.
Methods: A total of 48 male SD rats were randomized into a sham-operation group, a model group, a transcutaneous auricular non-vagus nerve stimulation (tnVNS) group and a taVNS group, with 12 rats in each group. The suture-occluded method was adopted to prepare MCAO rat model. The auricular rim was stimulated in the tnVNS group and the concha stimulated in the taVNS group, 2 mA in intensity, 10 Hz in frequency, 30 min each time, once a day, for 14 days consecutively. The nerve functional assessment was recorded in each group. The expressions of nicotinic acetylcholine receptor (α7nAchR) in the cerebral ischemic penumbra and the spleen were detected by using Western blot. With the immunofluorescence, the expressions of GFAP and MAP2 were detected.
Results: After modeling, compared with the sham-operation group, the nerve functional score was increased in the model group, the tnVNS group and the taVNS group (P<0.01), suggesting the success of modeling. After treatment, the score was increased in the model group (P<0.01) as compared with the sham-operation group. Compared with the model group, the neurological deficit score was reduced in the taVNS group (P<0.01). Compared with the sham-operation group, GFAP expression was increased and MAP2 expression was reduced remarkably in the cerebral ischemic penumbra in the model group (P<0.05). In comparison with the model group, GFAP expression was reduced, while MAP2 expression was increased remarkably in the cerebral ischemic penumbra in the taVNS group (P<0.05). There were no significant differences in the abovementioned indexes between the model group and tnVNS group (P>0.05). The differences in the expression of α7nAchR in the cerebral ischemic penumbra and the spleen had no statistical significance among groups (P>0.05).
Conclusion: TaVNS is effective on neuroprotection in MCAO rats, which may be related to its function of inhibition of GFAP expression and promotion of MAP2 expression in the ischemic penumbra.
目的：观察经皮耳迷走神经刺激(taVNS)对大脑中动脉栓塞(MCAO)模型大鼠运动功能及缺血半暗带胶质纤维酸性蛋白(GFAP)、微管相关蛋白2(MAP2)表达的影响，探讨taVNS改善MCAO模型大鼠运动功能的作用机制。方法：雄性SD大鼠随机分为假手术组、模型组、耳缘-非迷走神经刺激(tnVNS)组、taVNS组，每组12只。采用线栓法制备MCAO大鼠模型。tnVNS组刺激部位为耳缘区，taVNS组刺激部位为耳甲区，强度为2 mA，频率为10 Hz，每次30 min，1次/d，治疗14 d。按照Bederson神经缺损评分法记录各组大鼠神经功能缺损评分，Western blot法检测大鼠大脑缺血半暗带及脾脏中α7烟碱型乙酰胆碱受体(α7nAchR)的表达水平，免疫荧光法检测大鼠大脑缺血半暗带区GFAP、MAP2的表达水平。结果：造模后与假手术组比较，模型组、tnVNS组、taVNS组神经功能缺损评分升高(P<0.01)。治疗后，与假手术组比较，模型组神经功能缺损评分升高(P<0.01)；与模型组比较，taVNS 组神经功能缺损评分降低(P<0.01)。与假手术组比较，模型组大脑缺血半暗带GFAP表达显著升高、MAP2表达显著降低(P<0.05)；与模型组比较，taVNS组GFAP表达显著降低，MAP2表达显著升高(P<0.05)。tnVNS组各指标与模型组比较的差异无统计学意义（P>0.05）。各组间大脑缺血半暗带和脾脏中α7nAchR表达比较，差异均无统计学意义(P>0.05)。结论：taVNS对MCAO大鼠具有神经保护作用，这可能是通过抑制缺血半暗带的GFAP表达，并促进缺血半暗带中MAP2的表达来实现的。.
Keywords: Astrocytes; Cholinergic anti-inflammatory pathway; Ischemic stroke; Neuroprotection; Transcutaneous auricular vagus nerve stimulation.