Effects of Space Radiation on Freezing in Mice following Yoked Controllable and Uncontrollable Footshock
Poster #: 184
Session/Time: A
Author:
Gian Fran Goboy
Mentor:
Laurie L Wellman, PhD
Research Type: Basic Science
Abstract
INTRODUCTION:
The planned mission to Mars will pose significant known hazards to astronauts in a variety of areas including exposure to space radiation. Astronauts likely will also be exposed to unknown hazards. Space radiation could alter the ability of astronauts to manage stressful events and emergencies that lie outside their normal duties. Controllability is an important factor shaping behavioral and neurobiological responses that may impact the ability of astronauts to cope with stress. In this study, we investigated how space radiation impacts fear memory formation and extinction in a mouse model of controllable and uncontrollable stress.
METHODS:
C57BL/6 male mice (18 wks old) were exposed to either space radiation (15cGy GCRsim; SR; n=10) or served as non-irradiated controls (SHAM; n=6) at Brookhaven National Laboratory and were then shipped to Eastern Virginia Medical School for study. Three months following irradiation, mice were assigned to either escapable stress (ES) or inescapable stress (IS) conditions. All ES and IS mice were exposed to two consecutive days of shock training (ST: 20 footshocks, 0.5 mA, 5.0 s max. duration, 1 min intervals) in a shuttlebox. The ES group had the ability to learn they could behaviorally terminate the footshock by moving to the opposite shuttlebox chamber; the yoked IS group could not control the shock. Termination of shock for an ES mouse also terminated the shock to its yoked IS mouse. Thus, a pair of mice received identical shock, but it was characterized as either controllable or uncontrollable based on ability to escape. On day 7, the mice underwent context re-exposure (CTX; 30 minutes with no shock, same context) and on day 21, extinction (EXT; 30 minutes with no shock, same context). Each session was recorded, and freezing behavior (complete cessation of moving except respiration) was analyzed as an index of fear responses using EthoVision behavioral analysis software.
RESULTS:
In SR mice, there were significant differences in freezing behavior between ES and IS groups during CTX and EXT; ES mice showed lower freezing levels similar to those of sham mice. SHAM mice showed no significant differences between ES and IS groups across any of the days. Data analyses between groups are ongoing.
CONCLUSION:
These data demonstrate that stressor controllability ameliorates freezing in irradiated mice. This suggests that being able to control stress may offset some of the negative effects of SR on stress-related fear learning and memory.
The planned mission to Mars will pose significant known hazards to astronauts in a variety of areas including exposure to space radiation. Astronauts likely will also be exposed to unknown hazards. Space radiation could alter the ability of astronauts to manage stressful events and emergencies that lie outside their normal duties. Controllability is an important factor shaping behavioral and neurobiological responses that may impact the ability of astronauts to cope with stress. In this study, we investigated how space radiation impacts fear memory formation and extinction in a mouse model of controllable and uncontrollable stress.
METHODS:
C57BL/6 male mice (18 wks old) were exposed to either space radiation (15cGy GCRsim; SR; n=10) or served as non-irradiated controls (SHAM; n=6) at Brookhaven National Laboratory and were then shipped to Eastern Virginia Medical School for study. Three months following irradiation, mice were assigned to either escapable stress (ES) or inescapable stress (IS) conditions. All ES and IS mice were exposed to two consecutive days of shock training (ST: 20 footshocks, 0.5 mA, 5.0 s max. duration, 1 min intervals) in a shuttlebox. The ES group had the ability to learn they could behaviorally terminate the footshock by moving to the opposite shuttlebox chamber; the yoked IS group could not control the shock. Termination of shock for an ES mouse also terminated the shock to its yoked IS mouse. Thus, a pair of mice received identical shock, but it was characterized as either controllable or uncontrollable based on ability to escape. On day 7, the mice underwent context re-exposure (CTX; 30 minutes with no shock, same context) and on day 21, extinction (EXT; 30 minutes with no shock, same context). Each session was recorded, and freezing behavior (complete cessation of moving except respiration) was analyzed as an index of fear responses using EthoVision behavioral analysis software.
RESULTS:
In SR mice, there were significant differences in freezing behavior between ES and IS groups during CTX and EXT; ES mice showed lower freezing levels similar to those of sham mice. SHAM mice showed no significant differences between ES and IS groups across any of the days. Data analyses between groups are ongoing.
CONCLUSION:
These data demonstrate that stressor controllability ameliorates freezing in irradiated mice. This suggests that being able to control stress may offset some of the negative effects of SR on stress-related fear learning and memory.