MgSO₄ Effects On The Proliferation Of The Hippocampal Dentate Gyrus Neurogenesis And The Ability Of Learning And Memorizing In Adult Rats With Radiation-induced Brain Injury

Objective:To explore the neuroprotective effect of magnesium sulfate(MgSO₄) in the dentate gyrus(DG) of the adult rats with brain injury induced by radiation and the relationship between the ability of learning and memorizing.Methods:Sprague Dawley rats(SD) were randomly divided into 3 groups:the experimental group[radiation combined with MgSO₄],the experimental control group[radiation combined with normal saline(NS)]and the blank control group[treat with NS only].The whole brain of SD rats were irradiated with a single vertical dose of 20Gy by 5MeV electron so as to get a model of radiation-induced brain injury.Proliferous cells were marked with 5-bromine deoxidizing uracil nucleoside(5-bromodeoxyuridine,BrdU) for the following three days after radiation,and Immunohistochemical method was applied to detected BrdU positive cells,then Stereological calculating method was used to count the total BrdU positive cells of DG.SD rats screened by Y maze tests were administrated with 10%MgSO₄(400 mg·kg-1) by slow intraperitoneal injection at four time points:1 d before radiation,30 min before radiation,immediately after radiation and continuous 5 d after radiation(once per day).7d,14 d and 28d after irradiation,the rats were trained by Y maze training for consecutive 3d respectively.And then,Immunohistochemical method was applied to check the BrdU possitive cells.Y maze performances were used to estimate the relationship between MgSO₄ and the ability of learning and memorizing,and the neuroprotective effect of MgSO₄.SD rats were administrated with 10%MgSO₄(400 mg·kg-1) by slow intraperitoneal injection at three time points:1 d before radiation,30 min before radiation and immediately after radiation.Neuroepthelial stem cell protein(Nestin) expression was observed by Immunofluorescence method at 2 hours after irradiation.Results:1.A few BrdU positive cells were visualized in the hippocampal detate gyrus of the blank control group.Compared with the blank control group,BrdU positive cells were markedly increased in DG in the experimental control group.The difference between the two groups has statistical significance(P＜0.05). 2.Y maze training:The Y maze performances in the blank control group were almost the same at different time points,so there was no statistical significance among groups. Compared with the blank control group,the Y maze performances of experimental control groups decreased and the difference was statistically significant(P＜0.05).Interfered with MgSO₄,the performance of 28 d group was obviously higher than 7 d,14 d group and the blank control group,the statistical differences were significant(P＜0.05).After Y maze training,further analysis was done by Immunohistochemical method and the results showed that BrdU possive cells of the experimental control group were much more than the blank control group at the same time point,and there was significant difference(P＜0.05).As time goes by,the BrdU positive cell number decreased gradually in the experimental control group,the BrdU positive cell number of the 7 d group was more than that of 14 d and 28 d group,and the statistical differences were significant(P＜0.05),but after the MgSO₄ interference,the BrdU positive cells in experimental group were fewer at each time than experimental control group and the statistical differences were significant(P＜0.05).3.Compared with the blank control group,Nestin positive cells in the hippocampal were increased obviously in the experimental group,especially the dentate gyrus and the differences were significant(P＜0.05).Compared with the experimental control group, Nestin positive cells in the hippocampal of the experimental group was decreased sharply. The statistical differences were significant(P＜0.05).Conclusion:1,The neurogensis in DG area can be enhanced in adult rats with radiation-induced brain injury,and cell proliferation was induced.2,MgSO₄ can promote and improve the recovery of learning and memorizing ability in adult rats with radiation-induced brain injury,and obviously reduce the proliferation of neurocyte in DG area.So MgSO₄ has good neuroprotective effect.3,MgSO₄ can obviously inhibit Nestin expression in the adult rats with radiation-induced brain injury,and obviously improve the neural energy metabolism and promote neuro function recovery.