Presentations

Abstract

Introduction:

Astronauts will be exposed to space radiation (SR) and undergo periods of social isolation (SI) during lengthy space expeditions like the planned Mars missions. Both stressors have the potential to impact the physical and mental health of astronauts, which could potentially impact mission performance and stress management. We have demonstrated that SR and SI have differential effects on sensorimotor performance, sleep, and fear-conditioned freezing behavior in male rats. It has yet to be determined whether these stressors have differential effects in males and females. In this project, we utilized balance beam (BB) and bilateral tactile adhesive removal (BTAR) tasks to assess potential sex differences in the effects of SR and SI on sensorimotor performance.

Methods:

Male and female outbred, Wistar strain rats served as subjects. Both sexes were 8-9 months old at the time of study. Prior to behavioral experiments, rats either received SR (15 cGy GCRsim), SI (visual barriers between cages), dual flight stressors (DFS; SR+SI) or were individually housed (as a control group; SHAM). Ninety days following SR, time and age-matched groups of rats began BB and BTAR tasks to assess gross and fine motor function. The BB task requires the rat to traverse a beam from a start platform to a goal platform within 120 seconds, and consists of five trials over the span of seven consecutive days, with the start platform moving 1 position further from the goal platform if they succeed (all four paws reach the goal platform), or 1 position closer to the goal platform if they fail (time out or fall off). The closest start position is position 1 and the furthest start position is position 4. The BTAR task requires the rat to remove an adhesive sticker applied to their forepaw within 120 seconds and consists of four trials alternating between the right and left paws over the span of four consecutive days. BB and BTAR data were analyzed using a two-way mixed-factor analysis of variance (ANOVA) tests with Treatment (Control, SI, SR, DFS) x Gender (Male or Female). Tukey's post-hoc multiple comparisons test was performed when indicated by a significant ANOVA. We focused on reporting differences between sexes within the same treatment groups, although differences within sexes between treatment groups were also examined.

Results:

BB data did not show differences in success rates between sexes. However, females in the SHAM, SI and DFS groups spent more time on the beam than did males, while males in the SHAM, SR, and DFS groups spent more trials in positions 2 and 3 than did females. Of interest, there were no significant differences in the amount of failed BB attempts between sexes. Interestingly, males in the SHAM, SI, and SR groups fell off the beam significantly more than females. BTAR data show similar results. All animals completed the BTAR task; however, males in the SHAM, SR, and DFS groups took longer to notice and to remove the sticker than females. Additionally, SHAM males had longer latency times (the time between noticing and removing the sticker) than females.

Conclusion:

This study has identified sex-dependent performance decrements. Both BB and BTAR tasks showed little variation in terms of task success; however, male rats had distinct performance decrements in task efficiency. Not only did they need more trials to succeed in the BB task, but they also fell off the beam more than did females, implying possible sex differences in impairments in sensorimotor and vestibular function. While females did not exhibit deficits in terms of failing the BB task, they did show deficits in efficiency, taking longer to traverse the beam than males. During the BTAR task, males took longer to notice and remove the sticker and had longer latency periods between noticing and removing the sticker than did females, also suggesting possible sex differences in impairments in fine motor function. This research suggests that male and female rats are both impacted by SI and SR, but how these stressors impact performance can be sex-dependent.