Sex Differences in Stress Responses and Stress Related Learning in Wistar Rats exposed to Social Isolation and Space Radiation
Poster #: 118
Session/Time: A
Author:
Zachary Norman Martin Luyo, BS
Mentor:
Larry D. Sanford, PhD
Research Type: Basic Science
Abstract
INTRODUCTION:
With the planned Mars missions, male and female astronauts will be traveling deeper into space for longer durations of time than ever before and will be exposed to spaceflight stressors including Social Isolation (SI) and Space Radiation (SR). Additionally, astronauts may encounter stressful situations they have never experienced before with potential sex differences in their ability to cope. In rodents, freezing behavior and stress-induced hyperthermia (SIH) are indexes of the stress response that can also be used to assess stress-related learning. Previous research in our lab has shown that male rats exhibit altered conditioned freezing and SIH when exposed to SI and SR. However, it is unknown whether the effects of SI and SR on stress responses and stress related learning differs in females. This project utilized a conditioned fear (CF) paradigm and wireless telemetry to investigate the effects of SI and SR using freezing and whole-body temperature as indices.
METHODS:
Male and female outbred, Wistar rats (8-9 months upon arrival) served as subjects. Animals were either individually housed (IH) as a control group (SHAM) or exposed to ground-based analogs of SI (IH with opaque barriers) or SR (15cGy GCRsim) independently or in combination (dual flight stressors, DFS). Five weeks prior to behavioral testing, animals were intraperitoneally implanted with wireless telemetry transmitters to record whole-body temperature. The CF paradigm consisted of Shock Training (ST, Day 0), Context (CTX, Day 7), and Extinction (EXT, Day 21) to assess fear responses, fear memory consolidation, and extinction learning, respectively. Temperature recordings were conducted prior to CF (baseline) as well as after ST, CTX, and EXT.
RESULTS:
All female treatment groups showed differences in freezing between ST and CTX or EXT. Additionally, female SR froze significantly less during EXT compared to CTX. Between sexes, female SHAM and SI rats froze significantly more than their male counterparts during ST, CTX and EXT. However, DFS females froze significantly less than their male counterparts during ST. Females in all treatment groups had significantly higher body temperature for the first 90 minutes post-ST, -CTX and -EXT compared to baseline (with post-CTX and -EXT being significantly lower than post-ST). Between sexes, female SI body temperature was significantly lower during baseline compared to male SI. All female treatment groups had significantly lower whole-body temperatures compared to their male counterparts post-ST, -CTX and -EXT.
DISCUSSION:
This project demonstrates that spaceflight stressors (SI and SR) can alter freezing behavior and whole-body temperature in female rats when exposed to footshock. Analyses of males and females revealed that SI and SR differentially influence freezing and whole-body temperature between sexes. Additionally, SI and SR may produce synergistic effects in one sex that is not seen in the other. Taken together, these results suggest that spaceflight stressors differentially impact the stress response and stress related learning in males and females in ways that may need to be considered when planning deep space missions.
With the planned Mars missions, male and female astronauts will be traveling deeper into space for longer durations of time than ever before and will be exposed to spaceflight stressors including Social Isolation (SI) and Space Radiation (SR). Additionally, astronauts may encounter stressful situations they have never experienced before with potential sex differences in their ability to cope. In rodents, freezing behavior and stress-induced hyperthermia (SIH) are indexes of the stress response that can also be used to assess stress-related learning. Previous research in our lab has shown that male rats exhibit altered conditioned freezing and SIH when exposed to SI and SR. However, it is unknown whether the effects of SI and SR on stress responses and stress related learning differs in females. This project utilized a conditioned fear (CF) paradigm and wireless telemetry to investigate the effects of SI and SR using freezing and whole-body temperature as indices.
METHODS:
Male and female outbred, Wistar rats (8-9 months upon arrival) served as subjects. Animals were either individually housed (IH) as a control group (SHAM) or exposed to ground-based analogs of SI (IH with opaque barriers) or SR (15cGy GCRsim) independently or in combination (dual flight stressors, DFS). Five weeks prior to behavioral testing, animals were intraperitoneally implanted with wireless telemetry transmitters to record whole-body temperature. The CF paradigm consisted of Shock Training (ST, Day 0), Context (CTX, Day 7), and Extinction (EXT, Day 21) to assess fear responses, fear memory consolidation, and extinction learning, respectively. Temperature recordings were conducted prior to CF (baseline) as well as after ST, CTX, and EXT.
RESULTS:
All female treatment groups showed differences in freezing between ST and CTX or EXT. Additionally, female SR froze significantly less during EXT compared to CTX. Between sexes, female SHAM and SI rats froze significantly more than their male counterparts during ST, CTX and EXT. However, DFS females froze significantly less than their male counterparts during ST. Females in all treatment groups had significantly higher body temperature for the first 90 minutes post-ST, -CTX and -EXT compared to baseline (with post-CTX and -EXT being significantly lower than post-ST). Between sexes, female SI body temperature was significantly lower during baseline compared to male SI. All female treatment groups had significantly lower whole-body temperatures compared to their male counterparts post-ST, -CTX and -EXT.
DISCUSSION:
This project demonstrates that spaceflight stressors (SI and SR) can alter freezing behavior and whole-body temperature in female rats when exposed to footshock. Analyses of males and females revealed that SI and SR differentially influence freezing and whole-body temperature between sexes. Additionally, SI and SR may produce synergistic effects in one sex that is not seen in the other. Taken together, these results suggest that spaceflight stressors differentially impact the stress response and stress related learning in males and females in ways that may need to be considered when planning deep space missions.