Radiobiological response of rat hippocampus irradiated with gamma knife

Objective To investigate the effect of Leksell gamma knife irradiation on normal rat hippocampus through magnetic resonance imaging (MRI) and ultra-structure and analyze the gene expression profile of the rat hippocampus before and after the irradiation of the Leksell gamma knife.Methods The normal rats were irradiated with doses of 20,40,60 and 100 Gy,and 4-mm isocenters were used to cover the right hippocampus.MRI was performed at 3rd,5th and 7th month after radiosurgery with gamma knife.Rat was killed and the brain was removed to receive ultra-structural examination at 3rd month after irradiation under electron microscope.Meanwhile,we used gene chip to investigate the expression profile of genes and their function in the rats 3 months after irradiation with 25 Gy and 8-nm isocenters.Results After irradiation with 20 Gy,there were no obvious changes on MRI and ultra-structural examinations of the rat hippocampus.The damages of rat brain were aggravated with the increase of irradiation dose and the extension of duration.Mixed signals occurred in MRI,and electron microscopy showed neuronal pyknosis,endothelial cell damage,etc.The genes differentially expressed were categorized into different functions incIuding molecular function,biological process,cellular component,etc.Conclusion The effect of gamma knife on brain tissue appeared gradually with the extension of time and the increase of irradiation dose.The microarray analysis can screen the genes differentially expressed before and after irradiation,and classify the differentially expressed genes functionally. Key words: Gamma Knife ;  Hippocampus ;  Gene expression ;  Microarry analysis