The Influence Of MgSO₄ On The Expression Of C-fos Gene In The Hippocampus And The Learning And Memory Abilities Of Rats With Radiation Induced Brain Injuries

To explore the influence of Mg²⁺on the expression of c-fos gene in the hippocampus and the learning and memory abilities of rats with radiation induced brain injuries,and to approach the neuroprotection function of Mg²⁺ to radiation induced brain injuries and its mechanism,SD rats were randomly divided into 3 groups:the experimental group,the experimental control group and the blank control group.A radiation induced brain injuries model was set by a single vertical 5 MeV 20 Gy radiation to the whole brain of the rat and evaluated by the indexes of the hair-shedding of radiation area,the nervous system syndrome and the histological changes of the hippocampus within 30 days after radiation.10%MgSO₄(400 mg·kg^-1)was slowly administrated by intraperitoneal injection at three time points:1 day before radiation,30 minutes before radiation and immediately after radiation.The rat was sacrificed either 2 hours after radiation for detecting the expression of c-fos gene by immunofluorescence or 7 days,14 days or 28 days after radiation for Y maze training.The training was carried out 3 days before sacrifice and Y maze memory test was conducted at the right day of sacrifice.The rat was sacrificed 2 hours after memory test for detecting the expression ofc-fos gene by immunofluorescence.The experimental control group was injected by normal saline of equal dose instead of MgSO₄,and the blank control was treated by false radiation.It was showed that:there was exactly defined hair-shedding area on the brain skin of the rat after radiation and the neurons were arranged loosely in the dentate gyrus(DG)of hippocampus and the DG was badly demarcated; the Fos-positive cells in the DG of the two radiation groups were increased significantly(P＜0.01)compared to those of false radiation group,while the cells of the experimental group were decreased significantly(P＜0.01) compared to those of the experimental control group;the Y maze training showed that rats of the experimental group survived for 28 days were significantly better than those of the experimental control group(P＜0.01) and accordingly,the Fos-positive cells were significantly increased in the former group than the latter one(P＜0.01).But there was no difference between the groups survived for 7 or 14 days and the experimental control group in Y maze test and Fos expression in the DG.It indicated that the neurons in the DG of the hippocampus were decreased in the rat with radiation induced brain injuries,but little abnormal nervous system syndrome was shown,so the whole brain radiation model was real and reliable;Mg²⁺could evidently inhibit the expression of c-fos gene in DG of rats with radiation induced brain injuries;Mg²⁺could evidently improve the ability of learning and memory of rats with radiation induced brain injuries at the late recovery period.