RESUMO
The planned missions to the Moon and Mars will present more significant health challenges to astronauts compared to low earth orbit missions. During deep space missions, astronauts will be constantly exposed to Space radiation (SR). Multiple rodent studies suggest that < 25â¯cGy of SR impairs performance in executive functions, which play a key role in advanced cognitive processes, but also regulate response inhibition and impulse control. There is the possibility that SR exposure may exacerbate aberrant behaviors evoked by psychological stress related to exposure to isolated and confined (ICE) hostile environment or independently induce additional aberrant behaviors. This study has determined that female Wistar rats exposed to 10â¯cGy of 250â¯MeV/n He had an increased risk taking propensity (RTP)\compared to shams. The increased RTP of the He-exposed rats was associated with significantly increased reaction times during the trials, suggesting a SR-induced loss of processing speed. The response times of the He-exposed rats were even further reduced in trials that immediately followed a loss, raising the possibility that conflict and interference avoidance may be impaired after SR exposure. Whether these findings occur following other types of SR exposure, and/or in male rats remains to be determined.
RESUMO
The proposed Mars missions will expose astronauts to long durations of social isolation (SI) and space radiation (SR). These stressors have been shown to alter the brain's macrostructure and microenvironment, including the blood-brain barrier (BBB). Breakdown of the BBB is linked to impaired executive functions and physical deficits, including sensorimotor and neurocognitive impairments. However, the precise mechanisms mediating these effects remain unknown. Additionally, the synergistic effects of combined exposure to SI and SR on the structural integrity of the BBB and brain remain unknown. We assessed the BBB integrity and morphology in the brains of male rats exposed to ground-based analogs of SI and SR. The rats exposed to SR had enlarged lateral ventricles and increased BBB damage associated with a loss of astrocytes and an increased number of leaky vessels. Many deficits observed in SR-treated animals were attenuated by dual exposure to SI (DFS). SI alone did not show BBB damage but did show differences in astrocyte morphology compared to the Controls. Thus, determining how single and combined inflight stressors modulate CNS structural integrity is crucial to fully understand the multiple pathways that could impact astronaut performance and health, including the alterations to the CNS structures and cell viability observed in this study.
RESUMO
Future NASA missions will require astronauts to travel farther and spend longer durations in space than ever before. This will also expose astronauts to longer periods of several physical and psychological challenges, including exposure to space radiation (SR) and periods of social isolation (SI), which could have unknown negative effects on physical and mental health. Each also has the potential to negatively impact sleep which can reduce the ability to cope with stressful experiences and lead to sensorimotor, neurocognitive, and physical deficits. The effects of SI and SR on gross motor performance has been shown to vary, and depend on, individual differences in stress resilience and vulnerability based on our established animal model in which stress produces different effects on sleep. In this study, the impact that SI and SR, either alone or together, had on fine motor skill performance (bilateral tactile adhesive removal task (BTAR)) was assessed in male rats. We also examined emotional, exploratory, and other off-task behavioral responses during testing and assessed whether sensorimotor performance and emotion varied with individual differences in resilience and vulnerability. BTAR task performance was differentially impacted by SI and SR, and were further influenced by the stress resilience/vulnerability phenotype of the rats. These findings further demonstrate that identifying individual responses to stressors that can impact sensorimotor ability and behavior necessary to perform mission-related tasks will be of particular importance for astronauts and future missions. Should similar effects occur in humans, there may be considerable inter-individual variability in the impact that inflight stressors have on astronauts and their ability to perform mission-related tasks.