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Dementia Astronautica: A Possible Outcome of Long-Duration Space Missions?     PM Cummings, MD¹, A Obenaus, PhD².    ¹Department of Pathology, Division of Neuropathology, University of Virginia, Charlottesville, VA. ²Radiation Medicine, Loma Linda University Medical Center, Loma Linda, CA.

Radiation exposure is a major health hazard associated with long-duration space missions. Of particular concern is the effect of high-energy high-charge (HZE) particles on the central nervous system (CNS) of astronauts.  Damage to sensitive regions of the brain such as the hippocampus may have important implications on behavior and memory functions.  Astrocytes are important first responders to CNS injury and express glial fibrillary acidic protein (GFAP) when activated, a process termed gliosis or reactive astrocytosis. Often this process is accompanied by delayed axonal degeneration and subsequent neuronal loss. In our current study we set out to determine the effects of HZE on the CNS of rats exposed to head-only irradiation (600 MeV/n, 56Fe) in a single fraction of 0, 1, 2, 4, Gy. Rats were euthanized at 1-week and 1, 6, and 12-months post exposure. GFAP immunohistochemistry was used to determine the astrocytic response and quantification was performed using image densitometry. A modified Gallyas silver stain was used to detect degenerating axons. We found increased gliosis which was progressive in severity over all time periods within the hippocampus of experimental animals compared to controls. In addition, we identified degenerating axons within the fornix and in other regions of the limbic system with a similar time dependence. These lesions are similar to those seen in patients with Alzhiemer’s disease. Given these findings it is possible that the performance of astronauts exposed to HZE on long-duration space missions may be compromised by CNS lesions similar to those seen in patients with neurodegenerative diseases.