Effects of 17Beta-estradiol on cognitive performance of ovariectomized female rats exposed to 56Fe particles

Authors: RABIN, BERNARD M. - University Of Maryland; CARRIHILL-KNOLL, KIRSTY L. - University Of Maryland; LONG, LAUREN V. - University Of Maryland; PITTS, STEVEN C. - University Of Maryland; Shukitt-Hale, Barbara

Submitted to: Journal of Behavioral and Brain Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2013
Publication Date: 2/27/2013
Citation: Rabin, B., Carrihill-Knoll, K., Long, L., Pitts, S., Shukitt Hale, B. 2013. Effects of 17Beta-estradiol on cognitive performance of ovariectomized female rats exposed to 56Fe particles. Journal of Behavioral and Brain Science. 3:67-73.

Interpretive Summary: 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 of this radiation on central nervous system function and cognitive performance in female subjects. Because estrogen has been shown to protect brain cells, the present experiments were designed to evaluate whether susceptibility to neurocognitive decline would change if estrogen was present at the time of exposure to iron radiation in female rats. After removing the ovaries from female rats, capsules containing a form of estrogen (estradiol 17 beta) or vehicle were implanted three days prior to exposure to iron particles. Cognitive performance was evaluated using the elevated plus-maze to measure baseline anxiety; novel object recognition memory to measure learning and memory; and operant responding to measure responsiveness to environmental contingencies. The results indicated the estrogen does not function as a neuroprotectant to minimize the cognitive effects of exposure to iron radiation. 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 particles on the performance of specific cognitive tasks.

Technical Abstract: On exploratory class missions to other planets astronauts will be exposed to types and doses of radiation (HZE particles) 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 HZE particles 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 estradiol 17 beta 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 the elevated plus-maze to measure baseline anxiety; novel object recognition memory to measure learning and memory; and operant responding on an ascending fixed-ratio schedule to measure 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.