en Radiation Biology Radiation Biology تحقيق بديع Original Research <p><strong>Background:</strong> Ionizing radiation causes cognitive impairment in adult brain. However, the effects of various irradiation protocols with fractionated fixed total dose on hippocampal function have not yet been studied. <strong>Materials and Methods:</strong> Fractionated whole brain irradiation with a total dose of 36 Gy was performed according to the following protocols: 2Gy-18 fractions (2Gy*18), 4Gy-9 fraction (4Gy*9) and 6Gy-6 fractions (6Gy*6). Changes in spatial memory were studied in Morris water maze tests at 12th and 17th day after irradiation with a hidden platform and at 38th day after irradiation without a platform. Levels of expression of brain derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) genes were evaluated using qPCR.<strong> Results:</strong> Expression of genes of neurotrophic factors (BDNF and VEGF) was decreased at 4^th and 8^th week after irradiation, the decrease depended on fractionation. The Morris water maze test with a hidden platform showed improvement in long-term spatial memory at 12^th and 17^th day after irradiation. In the Morris water maze test without platform cognitive deficit was detected only in 6Gy*6 group at 4^th week after irradiation. <strong>Conclusion:</strong> Our study shows that different fractionation protocols affect hippocampal functions differently, and that the greatest negative impact has the protocol with the maximum single dose. In addition, decrease in expression of genes of neurotrophic factors might play an important role in cognitive impairment.</p> Fractionated radiation, cognitive dysfunction, spatial memory, VEGF, BDNF 157 164 http://ijrr.com/browse.php?a_code=A-10-1-554&slc_lang=en&sid=1 Y.A. Zorkina zrkyana@gmail.com 790031947532846009760 790031947532846009760 Yes VP Serbsky National Research Center For Social and Forensic Psychiatry, Department of Basic and Applied Neurobiology, Kropotkinskiy side street 23, 119034, Moscow, Russian Federation E.A. Zubkov 790031947532846009761 790031947532846009761 No VP Serbsky National Research Center For Social and Forensic Psychiatry, Department of Basic and Applied Neurobiology, Kropotkinskiy side street 23, 119034, Moscow, Russian Federation Z.I. Storozheva 790031947532846009762 790031947532846009762 No VP Serbsky National Research Center For Social and Forensic Psychiatry, Department of Basic and Applied Neurobiology, Kropotkinskiy side street 23, 119034, Moscow, Russian Federation G.E. Gorlachev 790031947532846009763 790031947532846009763 No Burdenko Neurosurgery Institute RAMS, Department of Radiology and Radiosurgery, 4th Tverskaya-Yamskaya st. 16, 125047, Moscow, Russian Federation A.V. Golanov 790031947532846009764 790031947532846009764 No Burdenko Neurosurgery Institute RAMS, Department of Radiology and Radiosurgery, 4th Tverskaya-Yamskaya st. 16, 125047, Moscow, Russian Federation V.P. Chekhonin 790031947532846009765 790031947532846009765 No VP Serbsky National Research Center For Social and Forensic Psychiatry, Department of Basic and Applied Neurobiology, Kropotkinskiy side street 23, 119034, Moscow, Russian Federation