The Activation Of Ephrinb1/EPHB2/MAP2/NMDAR Pathway Participating In The Promotion Effect On Neurogenesis Caused By Transcranial Direct Current Stimulation In Cerebral Ischemia Mice

OBJECTIVE: To investigate the role of erythropoietin-producing hepatocellular ligand b1(ephrinb1)/receptor B2(EPHB2)/microtubule associated proteins2(MAP2)/N-methyl-D-aspartate(NMDAR)signaling pathway in hippocampal endogenous neurogenesis,and discuss the positive effects and mechanisms of transcranial direct current stimulation(tDCS)after cerebral ischemia.METHODS: Cerebral ischemic models were established with bilateral common carotid artery occlusion(BCCAO)in clean grade male C57BL/6J mice(7~8 weeks).Mice were randomly divided into 4 groups:sham operation group(Sham),BCCAO group(Model),BCCAO + tDCS75 ?A group(tDCSL)and BCCAO + tDCS 150 ?A group(tDCSH).The learning and memory function of mice were assessed by Morris water maze(MWM)test.The pathological changes in the hippocampal CA1 region of mice were detected by HE staining.The hippocampal neurogenesis wasobserved by immunofluorescence staining through detecting the positive expression of BrdU,DCX and BrdU/NeuN.The mRNA and protein expressions of ephrinb1,EPHB2,MAP2,NMDAR subunits NR2 A and NR2 B in hippocampus were analyzed by qRT-PCR and Western blot.RESULTS:1.The role of ephrinb1/EPHB2/MAP2/NMDAR signaling pathway in hippocampal neurogenesis after cerebral ischemiaCompared with the sham group,the MWM test showed that the mice in the model group obviously took more time in searching the platform,indicating significant learning and memory dysfunction(P < 0.01).The HE staining showed that the cells in the hippocampal CA1 region of the model group were disordered,broken,and irregular,with obvious neuronal pathological damages(P < 0.01).Immunofluorescence results showed that BrdU,DCX and BrdU/NeuN positive expressions were increased in the dentate gyrus of hippocampus in the model group(P < 0.01),the qRT-PCR and Western blot tests showed that mRNA and protein expressions of ephrinb1,EPHB2,MAP2,NR2 A and NR2 B in hippocampus were significantly increased(P < 0.01).2.The effect of tDCS on hippocampal neurogenesis after cerebral ischemia and its relationship with ephrinb1/EPHB2/MAP2/NMDAR signaling pathwayCompared with the model group,the tDCSH treatment shortened thetime for searching the platform and improved learning and memory function in MWM test(P < 0.01),increased the number of normal neurons which were arranged neatly,reduced pathological damage in the CA1region(P < 0.01),promoted the hippocampal neurogenesis as the number of BrdU,DCX and BrdU/NeuN positive cells(P < 0.01)increased,as well as increased the expressions of ephrinb1,EPHB2,MAP2,NR2 A and NR2 B mRNA and protein(P < 0.01)in hippocampus,respectively.CONCLUSION:1)Endogenous neurogenesis can be promoted by cerebral ischemia but it is insufficient to improve learning and memory dysfunction.2)ephrinb1/EPHB2/MAP2/NMDAR signaling pathway is involved in the process of hippocampal endogenous neurogenesis after cerebral ischemia.3)tDCS can promote hippocampal endogenous neurogenesis and improve learning and memory dysfunction after cerebral ischemia.This effect may be related to the activation of ephrinb1/EPHB2/MAP2/NMDA signaling pathway.