|Rabin, Bernard - University Of Maryland|
|Carrihill-knoll, Kirsty - University Of Maryland|
|O'conor, Shannon - University Of Maryland|
|Miller, Marshall - Duke University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/13/2017
Publication Date: 1/22/2018
Citation: Rabin, B.M., Carrihill-Knoll, K.L., O'Conor, S., Miller, M.G., Shukitt Hale, B. 2018. Effects of exposure to HZE particles on the cognitive performance of ovariectomized and intact female rats. Meeting Abstract. 2018 NASA Human Research Program Investigators Workshop, Program #18428.
Technical Abstract: INTRODUCTION It is likely that both male and female astronauts will comprise the crew on exploratory class missions. Despite this, the majority of the research using animal models has utilized male subjects. However, the limited data currently available suggests that the cognitive effects of exposure to high-energy heavy ion (HZE) particles may be different in male and female subjects. The present experiment was designed to further evaluate the effects of exposure to HZE particles on the cognitive performance of ovariectomized and intact female rats. METHODS The subjects were ovariectomized and intact female rats approximately two months of age at the time of irradiation. The ovariectomized (OVX) subjects were given implants of estradiol (E2) or vehicle (V). This procedure results in relatively stable physiological levels of estradiol for 4-5 weeks. The rats were given head only exposures to 12C (290 MeV/n, 5, 10, 25 cGy) or 4He (300 MeV/n, 0.025, 0.05 cGy) particles. Following irradiation, the rats were shipped to UMBC for behavioral testing. Cognitive tests included novel object recognition (general learning and memory), novel location recognition (hippocampal-dependent learning and memory), and operant responding on an ascending fixed-ratio schedule (responsiveness to environmental contingencies and motivation to work for reward). All behavioral tests were conducted at least 2 months after irradiation so that the hormonal status of the OVX rats was the same, regardless of whether they were given E2 or V at the time of exposure. RESULTS The results indicated that the effects of exposure to HZE particles on the cognitive performance of female rats varied as a function of the specific particle (12C, 4He), hormonal status at the time of irradiation (intact, E2, V) and the specific task (novel object performance, operant responding). First, exposure to either 12C or 4He did not cause a reliable disruption of performance on the novel object task 2 month following exposure. Second, E2 at the time of exposure provided some degree of protection against the deleterious effects of exposure on general learning and memory. Third, on the operant task, the presence of E2 at the time of exposure did not prevent the disruption of cognitive performance by exposure to either 12C or 4He particles. In the non-OVX rats, exposure to both particles increased the responsiveness of the subject to the changes in reinforcement contingencies. DISCUSSION These results suggest that the effects of exposure to HZE particles on cognitive performance of female subjects are more variable than they are for males. While hormonal status at the time of irradiation may be a factor influencing the effects of exposure on cognitive performance, the effects are not consistent, but may vary as a function of the specific particle and task.