Document Type
Thesis
Date of Award
1981
Abstract
The purpose of the present study was to systematically evaluate the effects of repeated restraint stress on awake, slow-wave sleep (SWS), rapid-eye-movement (REM) sleep and total sleep time (TST) in the mouse. In contrast to the anecdotal notion that stress uniformly produces insomnia, it was hypothesized that stress induced sleep disruptions would vary as a function of the intensity and chronicity of stressor exposure. A repeated measure (i.e., chronicity) design crossed with three levels of stressor intensity was employed in order to test this hypothesis. Forty-eight male random-bred Swiss mice weighing between 25 and 35 grams were implanted with cortical electrodes for recording the electroencephalogram (EEG). Twelve subjects were randomly assigned to each of the four stress conditions (i.e., intensity): restraint by confinement (mild stress); partial restraint (moderate stress); full restraint (severe stress); and control. All animals were briefly anesthetized with ether, sleep deprived and food deprived for the daily two hour stress period. Sleep was recorded immediately following stressor exposure on the following days: baseline (day 0); post two hour restraint stress (days 1, 2, 4, 6, 8, 10); and recovery (day 11). In an effort to independently assess the intensity of the different restraint stress procedures, body weight, adrenal weight and fecal excretion were also recorded.Differential stress related sleep disruptions were observed to occur as a function of intensity and chronicity of stressor exposure. Most of the significant changes in this study were obtained within a single stress condition across time and not between groups on individual days. Acute (single 2 hour exposure) mild restraint resulted in no significant sleep changes compared to baseline. Chronic mild restraint stress was associated with a significant decrease in TST on day 8 (p < .01) compared to baseline. Exposure to chronic moderate restraint stress resulted in a significant decrease in REM sleep (p <.01) on stress days 2, 4, 6, and 8 compared to baseline. Chronic moderate restraint stress was also associated with increased awake time (p < .05) and significantly decreased SWS (p < .01), and TST (p < .01) on days 4, 6, and 8 compared to stress day 1. Exposure to chronic severe stress resulted in a decrease in REM on days 4 (p< .05), 6 (p < .01) and 8 (p < .05) compared to baseline. Only the chronic severe restraint condition exhibited a significant increase in SWS (p < .01) on stress day 2 compared to baseline. A significant increase in awake (p < .01) and significant decreases in SWS (p < .01) and TST (p < .01) on stress day 8 compared to stress day 1 were also observed in this condition. Thus for chronic stressor exposure, the observed decrease in REM sleep was more pronounced for the moderate condition compared to the severe condition. In addition, the increases in awake and decreases in SWS and TST compared to stress day I occurred earlier in the moderate condition. The body weight, adrenal weight, and fecal excretion measures yielded conflicting results with regard to the operationalization of stressor intensity. The results of this study indicate that acute exposure to brief moderate and severe restraint stress is accompanied by a transitory increase in SWS in the mouse (perhaps analogous to an increased need for sleep in human subjects). Continued moderate and severe stressor exposure is accompanied by sleep disruptions more characteristic of restless sleep (perhaps analogous to insomnia in human subjects). Decreased REM sleep was associated with acute and chronic exposure in both the moderate and severe stress conditions.
Recommended Citation
Weiler, Debra Lee, "Effects of Restraint Stress on Sleep in the Mouse." (1981). All ETDs from UAB. 7076.
https://digitalcommons.library.uab.edu/etd-collection/7076
Comments
MA - Master of Arts; ProQuest publication number 31751996