Presentations

Abstract

Introduction: During future proposed space expeditions to Mars, astronauts will be exposed to approximately 13cGy of space radiation (SR) annually. SR affects multiple systems in ways that can negatively impact mission performance including fine sensorimotor function. Our lab has shown that SR has differential effects on fine motor performance in male rats, but cross-species data are needed to fully understand and model the impact of SR in ways that are applicable to astronauts. In this study, we implemented the bilateral tactical adhesive removal (BTAR) task, a test of fine motor control, in mice to provide comparison data for prior studies in rats. We also describe modifications required to conduct BTAR in mice and are obtaining data for cross-species comparisons.

Methods: Male outbred, retired breeder C57BL/6 strain mice served as subjects. Animals were 8-9 months old at the start of the study. Prior to behavioral experiments, mice were either individually housed and received 15 cGy GCRsim (SR) or were individually housed (control group; SHAM). At least ninety days following irradiation, time and age matched groups of mice were assessed on the BTAR task during the 7th hour of "lights on". The task required the animal to remove an adhesive sticker applied to the hairless area on their forepaw within 120 seconds. Two trials a day for each forepaw (alternating right and left), with an intertrial interval of 5 minutes, was performed over 4 consecutive days.

Results: The utilization of the mouse model presented challenges. The equipment needed to be downsized; however, the smaller size introduced new difficulties. The mice were able to intentionally remove their sticker before being put into the observation container by clenching their forepaw, a behavior not previously observed in rats. Interestingly, this occurred more often by the SR mice than the SHAMs. Moreover, a greater number of personnel were needed to run the task and observe behaviors and when the sticker was noticed/removed. Unfortunately, the smaller size of the mouse and sticker resulted in null trials, where none of the personnel were able to detect when a sticker fell off. In addition, looking at observed behaviors, SHAM mice had nearly 16 times more recorded aggressions than their SR counterparts when placing the sticker, and both expressing more aggression than rats. While preliminary, data so far shows that SR mice have a shorter average notice and average removal time when compared to Resilient and Vulnerable SR and SHAM rats.

Conclusion: This study presents modifications and considerations needed to conduct the BTAR task in rats and mice and to perform cross-species comparisons. Some modifications were required due to the differences in size between rats and mice, but some may also be due to species-specific behaviors. Mice and rats are both used in ground-based models of spaceflight hazards including SR, and determining their similarities and differences will be critical for better understanding the effects of SR as NASA prepares astronauts for long-duration, deep space missions.