Effects of 17 β -Estradiol on Cognitive Performance of Ovariectomized Female Rats Exposed to Space Radiation

On exploratory class missions to other planets astronauts will be exposed to types and doses of radiation that are not experienced in low earth orbit. While it is likely that the crew will consist of both male and female astronauts, there has been little research on the effects of exposure to space radiation on central nervous system function and cognitive performance in female subjects. Because estrogen can function as a neuroprotectant, the present experiments were designed to evaluate whether or not the presence or absence of estrogen at the time of irradiation would affect the susceptibility to the neurocognitive effects of exposure to 56 Fe particles in female rats. Capsules containing 17β-estradiol or vehicle were implanted in ovariectomized rats three days prior to exposure 56 Fe particles (50 - 200 cGy, 1000 MeV/n). Cognitive performance was evaluated using novel object recognition memory to measure learning and memory and operant responding on an ascending fixed-ratio schedule to measure changes in motivation and in the responsiveness to environmental contingencies. The results indicated the estrogen does not function as a neuroprotectant to minimize the cognitive effects of exposure to 56 Fe particles. However, the presence/absence of estrogen at the time of irradiation could modulate the responsiveness of the subject to the disruptive effects of exposure to HZE particles on the performance of specific cognitive tasks.