Effects of Spaceflight Hazards on Stress-Related Learning: Implications for Astronaut Coping on Long Space Missions
Department
Department of Biomedical and Translational Sciences
Graduate Level
Doctoral
Graduate Program/Concentration
Biomedical Sciences
Presentation Type
Poster Presentation
Abstract
INTRODUCTION: Astronauts on the proposed Mars missions will be exposed to several spaceflight hazards including social isolation (SI) and space radiation (SR). These hazards, and their interactions, have the potential to impact many factors critical to mission success including the ability of astronauts to cope with unexpected stress. In this study, we utilized fear conditioning, a model of stress-related learning important for determining adaptive and maladaptive stress outcomes, to determine whether spaceflight hazards could have differential effects on stress responses in male and female rats. We examined freezing as an immediate behavioral response to stress and post-stress sleep to assess lasting effects.
METHODS: Male and female retired breeder, outbred, Wistar strain rats (8-9 months old) served as subjects. All were implanted for recording sleep via telemetry. Both males and females were randomly placed into one of the following groups: SHAM (single-housed, control group), SI (single-housed with visual barriers between cages), SR (single exposure to 15cGy simulated Galactic Cosmic Radiation), or a combination treatment (SI+SR; dual flight stressors, DFS). The fear conditioning paradigm consisted of one shock training (ST) day as well as two experimental days without footshock (context re-exposure (CTX) and extinction (EXT)) to assess adaptive learning. On ST day, time and age matched groups of rats were placed into the shock chamber and exposed to a 5 min pre-ST period, 20 min shock period (experiencing 1 footshock per min), and 5 min post-ST period (30 min total). Both 1 week (CTX) and 3 weeks (EXT) after ST, animals were re-exposed to the shock chamber for 30 min undisturbed. Each experimental day was video recorded to assess freezing behavior. Upon completion of each experiment day, animals were returned to their home cage for a 20h sleep recording to allow for comparisons across Baseline, Post-ST, Post-CTX, Post-EXT sleep.
RESULTS: Percent freezing was assessed throughout the 30 min recordings in 5 min blocks. Throughout all 6 blocks of ST, CTX, and EXT, female SHAM and SI rats froze more than their male counterparts. Conversely, male DFS froze significantly more than their female counterparts during Blocks 2 and 4 of ST. Additionally, during Block 1 of EXT, male SR rats froze significantly more than their female counterparts. Sleep data are still being analyzed.
CONCLUSION: This study shows that female SHAM and SI rats freeze more than their male counterparts throughout ST, CTX, and EXT. By comparison, SR and DFS had greater effects of freezing in males, particularly during EXT suggesting that SR may have greater effects on fear conditioned freezing in males. Ongoing work is analyzing how SI and SR impact sleep to see whether males and female rats exposed to spaceflight hazards differ in the longer-term effects of unexpected stress. Together, these data may provide insight into effects of ongoing spaceflight hazards on the ability of astronauts to cope with unexpected stress during long term space missions.
Keywords
Social isolation, Space radiation, Stress response
Effects of Spaceflight Hazards on Stress-Related Learning: Implications for Astronaut Coping on Long Space Missions
INTRODUCTION: Astronauts on the proposed Mars missions will be exposed to several spaceflight hazards including social isolation (SI) and space radiation (SR). These hazards, and their interactions, have the potential to impact many factors critical to mission success including the ability of astronauts to cope with unexpected stress. In this study, we utilized fear conditioning, a model of stress-related learning important for determining adaptive and maladaptive stress outcomes, to determine whether spaceflight hazards could have differential effects on stress responses in male and female rats. We examined freezing as an immediate behavioral response to stress and post-stress sleep to assess lasting effects.
METHODS: Male and female retired breeder, outbred, Wistar strain rats (8-9 months old) served as subjects. All were implanted for recording sleep via telemetry. Both males and females were randomly placed into one of the following groups: SHAM (single-housed, control group), SI (single-housed with visual barriers between cages), SR (single exposure to 15cGy simulated Galactic Cosmic Radiation), or a combination treatment (SI+SR; dual flight stressors, DFS). The fear conditioning paradigm consisted of one shock training (ST) day as well as two experimental days without footshock (context re-exposure (CTX) and extinction (EXT)) to assess adaptive learning. On ST day, time and age matched groups of rats were placed into the shock chamber and exposed to a 5 min pre-ST period, 20 min shock period (experiencing 1 footshock per min), and 5 min post-ST period (30 min total). Both 1 week (CTX) and 3 weeks (EXT) after ST, animals were re-exposed to the shock chamber for 30 min undisturbed. Each experimental day was video recorded to assess freezing behavior. Upon completion of each experiment day, animals were returned to their home cage for a 20h sleep recording to allow for comparisons across Baseline, Post-ST, Post-CTX, Post-EXT sleep.
RESULTS: Percent freezing was assessed throughout the 30 min recordings in 5 min blocks. Throughout all 6 blocks of ST, CTX, and EXT, female SHAM and SI rats froze more than their male counterparts. Conversely, male DFS froze significantly more than their female counterparts during Blocks 2 and 4 of ST. Additionally, during Block 1 of EXT, male SR rats froze significantly more than their female counterparts. Sleep data are still being analyzed.
CONCLUSION: This study shows that female SHAM and SI rats freeze more than their male counterparts throughout ST, CTX, and EXT. By comparison, SR and DFS had greater effects of freezing in males, particularly during EXT suggesting that SR may have greater effects on fear conditioned freezing in males. Ongoing work is analyzing how SI and SR impact sleep to see whether males and female rats exposed to spaceflight hazards differ in the longer-term effects of unexpected stress. Together, these data may provide insight into effects of ongoing spaceflight hazards on the ability of astronauts to cope with unexpected stress during long term space missions.