Chinese Journal of Clinical Anatomy ›› 2021, Vol. 39 ›› Issue (1): 41-48.doi: 10.13418/j.issn.1001-165x.2021.01.009

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Effects of relatively low dose of X-rays irradiation on adult cognition and hippocampal neurogenesis in juvenile mice

Zeng Lei1, Ji Taotao1, Zhou Lin1, Ke Xiangjie1, Zhao Yansheng1, Yang Bo1,2, Ren Boxu3, Tang Fengru4   

  1. 1. Department of Medical Imaging Center, Renmin Hospital, Hubei University of Medicine, Shiyan 442000, China; 2. Department of Radiology, Zhongnan Hospital of Wuhan University, Wuhan University, Wuhan 430071, China; 3. Yangtze University Health Science Center, Jingzhou 434023, China; 4. Radiation Physiology Laboratory, Singapore Nuclear Research and Safety Initiative, National University of Singapore 138062, Singapore 
  • Received:2019-09-17 Online:2021-01-25 Published:2021-01-27

Abstract: Objective To investigate the effects of relatively low dose of ionizing radiation on adult cognition and hippocampal neurogenesis in juvenile mice, and to illuminate the relationship between relatively low dose of irradiation, cognitive function and neurogenesis. Methods 20 Kunming mice were randomly divided into two groups at postnatal 21 days: a radiation group and a control group (P21) (n = 10 each group). The radiation group was exposured with an acute whole body irradiation with a dose of 5 Gy at P21, the normal control group was sham irradiated. The two groups of mice were weighed before being exposured, at 2 months old and 4 months old, respectively. At 4-month-old, each mouse was experimented with open field test (OPT), new object recognition experiment (NOR), fear conditioning test (FC) and Morris Water Maze test (MWM). Brain sections were then immunostaining for different markers including Ki67 (mark proliferation neuron), doublecortin (DCX, mark differentiation and migration neuron), calbindin (CB, mark interneuron), and parvalbumin (PV, mark interneuron) in hippocampal dentate gyrus (DG). Results  (1) In the body weight test, both at 2 and 4 months of age, the percentage of mice’ body weight gain in the radiated group was significantly lower than that of the control group (t=3.02, P<0.05; t=4.22, P<0.01). (2) There were no significant differences in the distance traveled within 5 min in OPT ( t=-1.672, P>0.05), the DI in NOR (t=0.753, P>0.05), the contextual memory related freezing time ( t=-0.885,P>0.05) and the clued memory related freezing time (t=0.15, P>0.05) in FC, the average escape latency (F=2.30,P>0.05) in MWM and the times of crossing platform (t=-1.07, P>0.05) between the two groups. (3) However, Ki67, DCX, CB and PV labeled neurons number in DG in irradiation group were significantly lower than that of the control group (Ki67, t=2.80, P<0.05; DCX, t=6.63, P<0.001;CB, t=3.75, P<0.01; PV, t=5.39, P<0.001). Conclusions (1) Relatively low doses (5 Gy) of ionizing radiation in juvenile stage cause slow body weight gain in mice. (2) Relatively low doses (5 Gy) of irradiation exposure to juvenile mice do not cause learning and memory disorder when mice were tested in adult, but it resulted in declining of neurogenesis in SGZ. (3) The decreasing of neurogenesis induced by irradiation includes injury of a series of processes such as proliferation, division, differentiation, migration and maturation of neurons. 

Key words:  , Ionizing radiation,  Cognition,  Hippocampus,  SGZ,  Neurogenesis

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