Neurobehavior Laboratory, Institute of Nuclear Medicine and Allied Sciences, Delhi 110054, India.
Exp Neurol. 2013 Oct;248:360-8. doi: 10.1016/j.expneurol.2013.06.005. Epub 2013 Jun 11.
Radiation-induced aberration in the neuronal integrity and cognitive functions are well known. However, there is a lacuna between sparsely reported immediate effects and the well documented delayed effects of radiation on cognitive functions. The present study was aimed at investigating the radiation-dose dependent incongruities in the early cognitive changes, employing two approaches, behavioral functions and diffusion tensor imaging (DTI). Six-month old female C57BL/6 mice were exposed to whole-body doses of 2, 5 and 8 Gy of γ-radiation and 24 h after exposure, the stress and anxiety levels were examined in the open-field test (OFT). Forty-eight hours after irradiation, the hippocampal dependent recognition memory was observed by the novel object recognition task (NORT), and the cognitive functions related to memory processing and recall were tested using the elevated plus maze (EPM). Magnetic resonance imaging, including diffusion tensor imaging (DTI) was done at 48-hour post-irradiation to visualize microstructural damage in brain parenchyma. Our results indicate a complex dose independent effect on the cognitive functions immediately after exposure to gamma rays. Radiation exposure caused short-term memory dysfunctions at lower doses, which were seen to be abrogated at higher doses, but the long-term memory processing was disrupted at higher doses. The hippocampus emerged as one of the sensitive regions to be affected by whole-body exposure to gamma rays, which led to profound immediate alterations in cognitive functions. Furthermore, the results indicate a cognitive recovery process, which might be dependent on the extent of damage to the hippocampal region. The present study also emphasizes the importance of further research to unravel the complex pattern of neurobehavioral responses immediately following ionizing radiation exposure.
已知电离辐射会导致神经元完整性和认知功能发生畸变。然而，目前对于辐射对认知功能的即时效应的报道较少，而对其延迟效应的报道却很多。本研究旨在通过两种方法（行为功能和弥散张量成像（DTI））研究早期认知变化中与辐射剂量相关的差异。将 6 月龄雌性 C57BL/6 小鼠暴露于全身 2、5 和 8Gy γ 射线中，在暴露后 24 小时，通过旷场实验（OFT）检查应激和焦虑水平。照射后 48 小时，通过新物体识别任务（NORT）观察海马依赖性识别记忆，使用高架十字迷宫（EPM）测试与记忆处理和回忆相关的认知功能。磁共振成像，包括弥散张量成像（DTI），在照射后 48 小时进行，以可视化脑实质的微观结构损伤。我们的结果表明，在暴露于伽马射线后立即对认知功能有复杂的非剂量依赖性影响。辐射暴露在较低剂量下会导致短期记忆功能障碍，而在较高剂量下则会消失，但长期记忆处理在较高剂量下会受到干扰。海马体是受全身γ射线照射影响的敏感区域之一，这导致认知功能立即发生深刻变化。此外，结果表明存在认知恢复过程，这可能取决于海马区损伤的程度。本研究还强调了进一步研究的重要性，以揭示电离辐射暴露后立即出现的神经行为反应的复杂模式。
