Raber Jacob, Rudobeck Emil, Campbell-Beachler Mary, Allen Antiño R, Allen Barrett, Rosi Susanna, Nelson Gregory A, Ramachandran Shaila, Turner Jennifer, Fike John R, Vlkolinsky Roman
a Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oregon 97239;
Radiat Res. 2014 Apr;181(4):362-8. doi: 10.1667/RR13347.1. Epub 2014 Mar 27.
The space radiation environment consists of multiple species of high-energy charge particles (HZE), including (56)Fe and (28)Si nuclei, that may impact neuronal cells, but their damaging effects on the central nervous system (CNS) have been poorly defined. Hippocampus-dependent memory functions have been shown to be highly sensitive to (56)Fe HZE particles, which poses a significant risk to the cognitive performance of astronauts during space missions. While low doses of (56)Fe radiation do not induce cell death of mature neurons, they affect synaptic plasticity in the CA1 region, the principal neuronal output of the hippocampal formation involved in memory formation. The effects of (28)Si on the CNS have not been defined. Compared to behaviorally naïve mice, cognitive testing might affect synaptic plasticity and the effects of (28)Si radiation on synaptic plasticity might be modulated by prior cognitive testing. Therefore, in the current study, we quantified the effects of whole-body (28)Si radiation (600 MeV/n, 0.25 and 1 Gy) on hippocampus-dependent contextual freezing and synaptic plasticity in the CA1 region of animals not exposed (behaviorally naïve mice) and animals exposed to the contextual freezing test (cognitively tested mice). In behaviorally naïve mice exposed to 0.25 and 1 Gy of (28)Si radiation, the magnitude of long-term potentiation (LTP) was enhanced. However, in mice irradiated with 0.25 Gy contextual fear conditioning was enhanced and was associated with a further enhancement of the LTP magnitude. Such increase in synaptic plasticity was not seen in cognitively tested mice irradiated with 1 Gy. Thus, low dose (28)Si radiation has effects on synaptic plasticity in the CA1 region of the hippocampus and these effects are modulated by cognitive testing in a contextual fear-conditioning test.
空间辐射环境由多种高能带电粒子（HZE）组成，包括（56）铁和（28）硅原子核，这些粒子可能会影响神经元细胞，但它们对中枢神经系统（CNS）的损害作用尚未明确界定。海马体依赖的记忆功能已被证明对（56）铁HZE粒子高度敏感，这对太空任务期间宇航员的认知表现构成了重大风险。虽然低剂量的（56）铁辐射不会诱导成熟神经元的细胞死亡，但它们会影响CA1区域的突触可塑性，CA1区域是参与记忆形成的海马结构的主要神经元输出部位。（28）硅对中枢神经系统的影响尚未明确。与未经行为训练的小鼠相比，认知测试可能会影响突触可塑性，并且（28）硅辐射对突触可塑性的影响可能会受到先前认知测试的调节。因此，在本研究中，我们量化了全身（28）硅辐射（600 MeV/n，0.25和1 Gy）对未暴露动物（未经行为训练的小鼠）和接受情境性冻结测试的动物（经过认知测试的小鼠）海马体依赖的情境性冻结和CA1区域突触可塑性的影响。在接受0.25和1 Gy（28）硅辐射的未经行为训练的小鼠中，长时程增强（LTP）的幅度增强。然而，在接受0.25 Gy辐射的小鼠中，情境性恐惧条件反射增强，并且与LTP幅度的进一步增强相关。在接受1 Gy辐射的经过认知测试的小鼠中未观察到这种突触可塑性的增加。因此，低剂量（28）硅辐射对海马体CA1区域的突触可塑性有影响，并且这些影响在情境性恐惧条件反射测试中会受到认知测试的调节。
