Male mice exposed to simulated deep space radiation experienced impaired spatial learning

Impact of Simulated Deep Space Radiation Exposure. An alluvial diagram depicting the effects of simplified GCR simulations (GCRsim), over time during future missions to Mars and lunar. The male cohort showed an increase in monocyte levels, impaired spatial learning, altered synapse levels, and increased microglia activation. The Male + PLX cohort had an increase in monocytes, but no other GCRsim impairments. Only minor microglia changes were noted. The monocyte levels in female mouse cohorts were higher than those of males, and there was no other GCRsim impairment. The male mouse cohort is denoted by a blue line. The male + PLX cohort (received microglia destroying agent) is denoted in green. The female mouse cohort is denoted in red. The x-axis indicates time and the y-axis GCRsim-induced decreases. Measurements show the time taken to perform an assay. (1) Analysis of tail vein blood for monocyte levels by flow cytometric analysis. (2) PLX administration microglia-depletion agent was administered in the chow. (3) The radial arm water maze was used to analyze spatial learning. (4) Microglia decrements and flow synaptocytometry were used to analyze microglia. Synapse analysis of female rodents was not done. Credit: Susanna Rossi, Created by Biorender
Researchers from multiple San Francisco facilities discovered that male mice exposed in radiation similar to the one used by humans on long-space missions had problems learning spatial patterns several months later. The group published their findings in Science Advances. It describes how they performed simulations and how it affected the mice. They also describe the ways they managed to avoid adverse effects.

Scientists will need to discover a way to shield them from cosmic radiation (GCR) if humans want to colonize Mars or the moon. Research has shown that the radiation can cause damage to the central nervous system. The researchers used lab mice to test radiation on their brains. The researchers instructed the mice to locate a platform under transparent water. They then tested their ability to do so using the instructions provided by the researchers. This test is used to measure changes in spatial learning over time.

Results showed that male mice made more mistakes after being exposed to the vaccine than control mice, but female mice were not affected. Further testing revealed that the brain's immune system activation was responsible for the impairment. Other tests did not show any signs of anxiety, social impairment, or problems with recognition memory, nor was there any evidence that the brain activated. However, the researchers did discover that the mice did not suffer spatial learning impairment if they were fed a diet designed to deplete microglia (immune brain cells) before they were exposed to GCR. They also discovered a biomarker that was associated with mice more susceptible to adverse effects from GCR exposure. This could be used to one day determine whether astronauts are more or less vulnerable to GCR-related problems.

Learn more about how deep space travel might affect the brain

Further information: Karen Krukowski and colleagues, The impact deep space radiation has on cognitive performance. From biological sex to countermeasures, Science Advances (2021). Journal information: Science Advances Karen Krukowski et al, The impact of deep space radiation on cognitive performance: From biological sex to biomarkers to countermeasures,(2021). DOI: 10.1126/sciadv.abg6702

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