Studies Of The Protective Effect And Mechanism Of MgSO₄ In The Early Phase Of Radiation-induced Brain Injury

Objective: Purpose of the test was to illustrate the neuroprotective effect of magnesium sulfate(MgSO4) in the early phase of radiation-induced brain injury and to explore the possible mechanism .Methods:Maturity Sprague-Dawley rats were randomly divided into 3 groups:experimental group [radiation combined with MgSO4], experimental control group[radiation combined with normal saline (NS)] and blank control group[treated with NS only].The hemi or whole brain of SD rats were irradiated with a dose of 20Gy using 5 MeV electron so as to establish two kinds of radiation-induced brain injury model.The hemi-brain radiation model: Fos protein expression was observed in the hippocampal formation of rat brain with immunofluorescence technique at 2h and 24h after irradiation;the learning and memory function was detected with Y-maze within 8 weeks after irradiation. The whole brain radiation model: the expression of intercellular surface adhesion molecule-1(ICAM-1) was measured serially with enzyme linked immunosorbnent assay (ELISA) within 14 days after irradiation. At the same time, the activity of myeloperoxidase(MPO) were measured by the absorption spectrometry. One way-ANOVA was used for analysis.Results:1.Compared with blank control group, Fos immunopositive cells in the hippocampal formation of experimental control group was increased markedly (P<0.05),the learning and memory results of Y-maze test of experimental group were declined significantly(P<0.05).Compared with experimental control group, the Fos immunopositive cells of experimental group were decreased significantly (P<0.05).The evaluation of cognitive functions with Y-maze of experimental group was much better than experimental control group, and the difference was significant(P<0.05).The observation of pathomorphology also supported the above results.2.Compared with blank control group, the expression of ICAM-1 and the activity of MPO in experimental control group were increased respectively since from the 1stday after the whole brain irradiation and maintain the high expression in the observation period (P<0.05).Experimental group had a result of lower ICAM-1 and MPO than experimental control group significantly.(P<0.05).Conclusions:1.MgSO4 can recover cognitive impairment in the early stage after irradiation of rats brain, and protect the hippocampal formation neurons by decreasing the expression of Fos protein.2. The upregulation of ICAM-1 and MPO can be regarded as sensitive indexes for the inflammatory reaction and blood brain barrier (BBB) damage in the early stage of brain injury induced by radiation. MgSO4 could reduce the inflammatory reaction and improve the function of blood brain barrier which might protected brains from radiation injury.