Individual and Synergistic Effects of Space Radiation and Social Isolation on the Sensorimotor Function of Female Rats
Abstract
Introduction:
Astronauts on future Mars missions will experience space radiation (SR) and social isolation (SI), which can impair sensorimotor functions in male rats. However, little is known about the potential effects of these stressors on sensorimotor function of female rats. We examined the individual and synergistic effects of SR and SI on sensorimotor performance of female rats during balance beam (BB) and bilateral tactile adhesive removal (BTAR) tasks, which assess gross and fine motor function, respectively.
Methods:
Female, Wistar strain rats (retired breeders) were obtained from Hilltop Lab Animals, Inc. Two subgroups were either individually housed without visual barriers (CONT; n=10) or with visual barriers (SI; n=13) between cages. Two other subgroups were subjected to 15cGy galactic cosmic radiation and either individually housed alone (SR; n=12) or received SR + SI (dual flight stressor, DFS; n=12). Behavioral tasks began 90 days after irradiation. BB ran for five trials a day across seven consecutive days. BTAR ran for four trials a day across four consecutive days. Two-way mixed-factor ANOVA with post-hoc tests were used for analyses.
Results:
During BB, there was a main effect of time but not of group. Specifically, there was increased success rates (p<0.001), decreased exploratory and disequilibrium behaviors (p<0.001 for both), and decreased failures due to time-out (p=0.012) and falls (p<0.001) over time. During BTAR, there was a main effect of group with the DFS (p=0.006) and SI (p=0.036) groups having longer average removal times than the SR group. There was also a main effect of group on behavior with the DFS and SI groups having significantly greater fear behavior than the control (p=0.001 and p=0.021, respectively) and SR (p=0.001 and p=0.001, respectively) groups. Moreover, there was a main effect of time with fear behaviors increasing on day 2 (p<0.001) and day 3 (p=0.015).
Conclusion:
Female rats showed fear and fine motor deficits after SI and DFS. Should similar differences occur in humans, multiple mitigation strategies may be needed to support astronauts' differential abilities to withstand mission related stressors.