Effect of Low-dose Radiation on Cognitive Function of Rats at Different Ages

Abstract

Purpose/Objective(s): It is known that radiation can induce cognitive dysfunction, but we still know little about the threshold of radiation dose. It turns out that 0.1 Gy radiation can modulate the expression of gene pathways involved in cognitive function. However, it isn’t clear whether 0.1 Gy whole brain irradiation can induce cognitive impairments. In this study, the relationship between 0.1 Gy exposure and cognitive function was investigated in rats at different ages. Materials/Methods: Thirty-two 1-month-old male Sprague-Dawley rats and thirty two six-month-old male Sprague-Dawley rats were divided randomly into 0.1Gy irradiated group and anesthesia control group. The rats were anesthetized, and then the whole brains were irradiated using 4MeV electron beams delivered by a linear accelerator. Behavioral tests were performed 3 months after irradiation in the order of open field, Morris water maze and passive avoidance test. The tests were used to evaluate the anxiety level, hippocampal dependent spatial learning and memory, and nonspatial learning and memory respectively. In Morris water maze, the place navigation test was conducted on the 1st to 4th day; while on the 5th day, the spatial probe test was done. Results: In the place navigation test of Morris water maze, six-month-old rats exhibited age dependent impairments in latency to find the hidden platform compared with the one-month-old rats. But radiation did not affect the six-month-old rats’ spatial learning and memory. Irradiated group (one month old) had significantly longer latency time than control group. Radiation did not have the effect on the anxiety level in the open field test, and there was no significant difference between groups in the latency of the passive avoidance. Conclusions: In present study, the hippocampal dependent spatial learning and memory capacity of the one-month-old rats was impaired by 0.1Gy whole brain irradiation, but it did not have the same effect on the six-month-old rats. These findings strongly suggest that low dose radiation is sensitive to induce cognitive impairments in younger rats. Author Disclosure: R. Sun: E. Research Grant; NSFC 81172128, NSFC 81102077, NSFC 30870740, Project of Postgraduate’s Innovation of Jiangsu Province cx10b-055z. L.Y. Zhang: E. Research Grant; NSFC 81172128, NSFC 81102077, NSFC 30870740, Project of Postgraduate’s Innovation of Jiangsu Province cx10b-055z. L.S. Chen: E. Research Grant; NSFC 81172128, NSFC 81102077, NSFC 30870740, Project of Postgraduate’s Innovation of Jiangsu Province cx10b-055z. Y. Tian: E. Research Grant; NSFC 81172128, NSFC 81102077, NSFC 30870740, Project of Postgraduate’s Innovation of Jiangsu Province cx10b-055z.