电离辐射致认知功能损伤大鼠模型的研究

Establishment of a rat model of cognitive impairment induced by ionizing radiation

目的对大鼠头部进行不同剂量照射,选取合适剂量建立电离辐射致认知功能损伤动物模型,为研究电离辐射致认知功能损伤发生机制、辐射防护剂研制等提供研究基础。方法将SPF级雄性大鼠20只随机分为对照组(C组)、10 Gy照射组(10 Gy IR组)、20 Gy照射组(20 Gy IR组)和30 Gy照射组(30 Gy IR组),每组各5只,C组不作处理,其余3组分别利用10 Gy、20 Gy和30 Gy电子线对不同组别SD大鼠头部进行单次照射,照射后30 d计算动物死亡率,利用Morris水迷宫对大鼠空间记忆能力进行检测,利用化学比色法检测大鼠脑皮质匀浆液中还原型谷胱甘肽(glutathione,GSH)、丙二醛(malondialdehyde,MDA),酶联免疫吸附法(enzyme-linked immuno Sorbent assay,ELISA)检测8羟基脱氧鸟苷(8-hydroxydeoxyguanosine,8-OHdG)含量,对经HE染色的大脑病理切片进行检测观察。结果 30 Gy IR组动物出现背毛不整齐,流涎等症状,头颈部发生严重的脱毛现象。照后30 d时,C组未见动物死亡,10 Gy IR组和20 Gy IR组动物死亡率为20%,30 Gy IR组动物死亡率为40%。Morris水迷宫定位航行实验结果显示30 Gy IR组在1～5 d的训练期中,潜伏期时间均高于其余三组且差异具有统计学意义(P<0. 05)。空间搜索实验显示30 Gy IR组较其余各组原平台象限停留时间显著缩短(P<0. 05);穿越平台次数显著减少(P<0. 05); 10 Gy IR组、20 Gy IR组、30 Gy IR组原平台象限游泳距离较C组均显著缩短(P<0. 05);氧化应激相关指标检测结果显示30 Gy IR组与C组相比GSH、8-OHdG、MDA浓度差异有统计学意义(P<0. 05),20 Gy IR组与C组MDA浓度差异有统计学意义(P<0. 05); HE染色切片发现20 Gy IR组和30 Gy IR组组织结构破坏较10 Gy IR组更加严重,出现组织细胞凋亡、坏死等显著的病理改变。结论本次实验结果提示对头部进行30 Gy单次照射可以成功建立大鼠认知功能障碍动物模型。

Objective To investigate the effects of exposure of the head of rats to different doses of ionizing radiation,to establish an appropriate animal model of cognitive function damage caused by such radiation,and to provide a research basis for studying the mechanism of cognitive function damage due to ionizing radiation and the development of radiation-protective agents.Methods Twenty male SPF rats were randomly and equally divided into a control group(C group),a 10 Gy irradiation group(10 Gy IR group),a20 Gy irradiation group(20 Gy IR group),and a 30 Gy irradiation group(30 Gy IR group).The group C was left untreated,while the other three groups were irradiated with 10,20,and 30 Gy electron beams,focused on the heads of the SD rats.The mortality of the animals was calculated using survival rates at 30 days after the irradiation and spatial memory was assessed using the Morris water maze.The concentrations of glutathione(GSH)and malondialdehyde(MDA)in rat brain cortical homogenate were determined by chemical colorimetry.An enzyme-linked immunosorbent assay(ELISA)was used to detect 8-hydroxydeoxyguanosine(8-OHdG).Brain pathological sections were analyzed by HE staining.Results The rats in the 30 Gy IR group exhibited irregular back hair,excessive salivation,and other symptoms,along with severe hair loss on the head and neck.At 30 days after the irradiation,no animal died in group C.The mortality rates of both the 10 and20 Gy IR groups were20%,while that of the 30 Gy IR group was 40%.The results regarding positioning and navigation in the Morris water maze experiment showed that the latency of the 30 Gy IR group in the 1-5-day training period was significantly higher than in the other three groups(P<0.05).The spatial search experiment showed that the residence time in the original platform quadrants of the 30 Gy IR group was significantly shorter than in the other groups(P<0.05);the number of platform crosses in this group was also significantly reduced(P<0.05).The swimming distances in the original platform for the 10,20,and 30 Gy IR groups were significantly shorter than for the group C(P<0.05).Moreover,the results of oxidative stress-related indicators showed that the concentrations of GSH,8-OHdG,and MDA in the 30 Gy IR group were significantly different from those in group C(P<0.05).The difference of MDA concentration between the20 Gy IR group and group C was statistically significant(P<0.05).Pathological examination also showed that the tissue damage of the20 and 30 Gy IR groups was more severe than that of the 10 Gy IR group,and there were significant pathological changes such as cell apoptosis and tissue necrosis.Conclusions This experiment shows that a rat model of cognitive dysfunction can be created by a single 30 Gy electron beam irradiation to the head.