Effect of transcutaneous auricular vagus nerve stimulation on the expressions of GFAP and MAP2 in ischemic penumbra of rats with middle cerebral artery ischemia

Abstract

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. 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. 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). 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.