Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA; Departments of Neurology and Radiation Medicine, Division of Neuroscience ONPRC, Oregon Health and Science University, Portland, OR 97239, USA.
Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, USA.
Life Sci Space Res (Amst). 2016 Jun;9:56-61. doi: 10.1016/j.lssr.2016.03.002. Epub 2016 Mar 22.
The space radiation environment includes energetic charged particles that may impact behavioral and cognitive performance. The relationship between the dose and the ionization density of the various types of charged particles (expressed as linear energy transfer or LET), and cognitive performance is complex. In our earlier work, whole body exposure to (28)Si ions (263 MeV/n, LET=78keV/μm; 1.6 Gy) affected contextual fear memory in C57BL/6J × DBA2/J F1 (B6D2F1) mice three months following irradiation but this was not the case following exposure to (48)Ti ions (1 GeV/n, LET=107keV/μm; 0.2 or 0.4 Gy). As an increased understanding of the impact of charged particle exposures is critical for assessment of risk to the CNS of astronauts during and following missions, in this study we used (40)Ca ion beams (942 MeV/n, LET=90keV/μm) to determine the behavioral and cognitive effects for the LET region between that of Si ions and Ti ions. (40)Ca ion exposure reduced baseline activity in a novel environment in a dose-dependent manner, which suggests reduced motivation to explore and/or a diminished level of curiosity in a novel environment. In addition, exposure to (40)Ca ions had sex-dependent effects on response to shock. (40)Ca ion irradiation reduced the response to shock in female, but not male, mice. In contrast, (40)Ca ion irradiation did not affect fear learning, memory, or extinction of fear memory for either gender at the doses employed in this study. Thus (40)Ca ion irradiation affected behavioral, but not cognitive, performance. The effects of (40)Ca ion irradiation on behavioral performance are relevant, as a combination of novelty and aversive environmental stimuli is pertinent to conditions experienced by astronauts during and following space missions.
空间辐射环境包括可能影响行为和认知表现的高能带电粒子。各种类型带电粒子（以线性能量转移或 LET 表示）的剂量与电离密度与认知表现之间的关系非常复杂。在我们之前的研究中，全身暴露于（28）Si 离子（263 MeV/n，LET=78keV/μm；1.6 Gy）会影响 C57BL/6J×DBA2/J F1（B6D2F1）小鼠在照射后三个月的情景恐惧记忆，但暴露于（48）Ti 离子（1 GeV/n，LET=107keV/μm；0.2 或 0.4 Gy）则不会。由于对带电粒子照射影响的深入了解对于评估宇航员在任务期间和之后的中枢神经系统风险至关重要，因此在这项研究中，我们使用（40）Ca 离子束（942 MeV/n，LET=90keV/μm）来确定 LET 介于 Si 离子和 Ti 离子之间的区域对行为和认知的影响。（40）Ca 离子暴露以剂量依赖的方式降低了在新环境中的基线活动，这表明对探索的动机降低了，或者对新环境的好奇心减弱了。此外，（40）Ca 离子暴露对电击反应有性别依赖性影响。（40）Ca 离子照射降低了雌性，但不降低雄性，小鼠对电击的反应。相比之下，（40）Ca 离子照射在本研究中使用的剂量下，对雌性和雄性的恐惧学习、记忆或恐惧记忆的消退均没有影响。因此，（40）Ca 离子照射影响行为表现，而不影响认知表现。（40）Ca 离子照射对行为表现的影响是相关的，因为新奇和厌恶环境刺激的结合与宇航员在任务期间和之后经历的情况有关。
