Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA.
Department of Environmental & Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, USA.
Behav Brain Res. 2020 Feb 3;379:112377. doi: 10.1016/j.bbr.2019.112377. Epub 2019 Nov 22.
To simulate the space radiation environment astronauts are exposed to, most studies involve acute exposures but during a space mission there will be chronic (long-lasting) exposures. To address this knowledge gap, a neutron irradiator using a Cf (Californium) source was used to generate a mixed field of neutrons and photons to simulate chronic, low dose rate exposures to high LET radiation. In the present study, we assessed the effects chronic neutron exposure starting at 60 days of age on behavioral and cognitive performance of BALB/c female and C3H male mice at 600 and 700 days of age as part of an opportunistic study that took advantage of the availability of neutron and sham-irradiated mice from a radiation carcinogenesis experiment. There were profound dose- and time point-dependent effects of chronic neutron exposure. At the 600-day time point, irradiated BALB/c female mice showed improved nest building at all three doses. At the 700-day, but not 600-day, time point slightly but significantly increased body weights were seen in C3H male mice exposed to 0.118 Gy. At the 600-day time point BALB/c female mice irradiated with 0.2 Gy did, like sham-irradiated, not show preferential exploration of the novel object that was seen in mice irradiated with 0.118 or 0.4 Gy. In C3H male mice exposed to 0.4 Gy and at the 600-day time point, increased measures of anxiety were observed on days 1 and 2 in the open field. Thus, different outcome measures show distinct dose-response relationships, with some anticipated to worsen performance during space missions, like increased measures of anxiety, while other anticipated to enhance performance, such as increased nest building and object recognition.
为了模拟宇航员在太空中所暴露的辐射环境，大多数研究都涉及急性暴露，但在太空任务中，还会存在慢性（长期）暴露。为了弥补这一知识空白，我们使用 Cf（锎）源的中子辐照器产生了中子和光子的混合场，以模拟慢性、低剂量率、高 LET 辐射的暴露。在本研究中，我们评估了从 60 天龄开始慢性中子照射对 BALB/c 雌性和 C3H 雄性小鼠的行为和认知表现的影响，这是一项利用来自辐射致癌实验的中子和假照射小鼠的可用性进行的机会性研究的一部分。慢性中子照射存在显著的剂量和时间依赖性影响。在 600 天时间点，照射的 BALB/c 雌性小鼠在所有三个剂量下均表现出改善的筑巢行为。在 700 天时间点，而不是 600 天时间点，暴露于 0.118 Gy 的 C3H 雄性小鼠的体重略有但显著增加。在 600 天时间点，接受 0.2 Gy 照射的 BALB/c 雌性小鼠，与假照射的小鼠一样，没有表现出对 0.118 或 0.4 Gy 照射的新物体的优先探索。在暴露于 0.4 Gy 的 C3H 雄性小鼠中，在 600 天时间点，在开放场的第 1 和第 2 天观察到焦虑程度增加的措施。因此，不同的结果测量方法显示出不同的剂量-反应关系，一些预期会在太空任务中恶化表现，例如增加焦虑程度，而另一些则预期会增强表现，例如增加筑巢和物体识别。
