| Objective: 1) After whole brain irradiation on the rats with differentdose-fraction regimens which biological effective doses were equal, the effect of themulti-fractionation on the rats tissue by observing the weight and nervous systemsymptoms and signs were investigated. 2) Using the neutral single cell gelelectrophoresis (SCGE) to detect DNA damage of the peripheral blood lymphocyte ofrates of each group, discussed the application of SCGE in brain radiation injury. 3)Comparing damage of the rat brain by detecting the contents of malondialdehyde(MDA) after the brain tissue homogenate.4) Observing the changes of the brainpathomorphology of each group with the Hematoxylin-eosin (HE) staining.Methods: 160 animals were randomized into 4 groups of 40 animals :1) controlgroup, without any intervention; 2) single high-dose group , 6MV-X,14.5Gy, wholebrain irradiation;3) multiple high-dose group, 6MV-X, 5.4Gy×6f; 4) conventionalfractionation group , 6MV-X, 2Gy×30f, 1f/d, 5f/w, whole brain irradiation. Allanimals were reared under the same conditions and treatment. Each group had asingle cell gel electrophoresis after irradiation, weighed every other week, and scoredon neurological behavior. After irradiation in a day, 1 week, 1 month, 3 months, 6months, MDA contens of brain tissue were tested and brain pathology specimenswere made on every observation point. Statistical evaluation was carded out. Usingone-way ANOVA, and repeated measures ANOVA.Experimental data was discriptedby mean±standard deviation((?)±s),P＜0.05, the comparison between the differencewas statistically significant.Results: 1) conventional observation: in the course of the experiment, seven ratsdied in the process of irradiation. The reasons perhaps were the poor posture in theprocess of anesthesia, and died of suffocation. During the observation time 6 rats died,without pathological analysis, which were excluded from the experiment. 1 monthafter irradiation, shed and skin ulceration were found in the head of the rats. Duringthe experiment weight of the rats showed no obvious differences, there was no statistical significance.2) neurological scores: up to the end of the experiment, the ratsphysical activities were normal ,the score was statistical analysised revealed nosignificant difference. 3) Single cell gel electrophoresis: irradiation on the wholebrain of the rats led to DNA double-strand of peripheral blood lymphocytebreak. DNA damage of single high-dose group was more serious than the others, andinjury of conventional fractionation group was the lightest. 4) MDA: MDA of braintissue began to increase one day after irradiatioin, with single hige-dose group higherthan multiple high-dose group, and the conventional group the lowest. 3 months afterirraditon, the DNA of each group was no statistically significant. 5) Pathology: cellswelling, loss of the typical multi-level and eccentric nucleus interstitial edema wasobserved. Blood-brain barrier was changed with vafing degrees. Damage in eachgroup under optical microscope had no obvous distinction.Conclusion: After whole brain irradiation with different dose-fractioinregimens which biological effective doses are equal, in early stage, brain injury ofsingle high-dose is more serious than that of multiple high-does and the response ofconventional fractionation group is the lightest. Late reaction is no significantdifference.
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