Date of Award

Spring 1-1-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Integrative Physiology

First Advisor

Monika Fleshner

Second Advisor

Daniel Barth

Third Advisor

Christopher Lowry

Fourth Advisor

Douglas Seals

Fifth Advisor

Kenneth P. Wright

Abstract

Exposure to stressors can trigger fight or flight behavioral responses and dynamic physiological changes that are highly adaptive and function together to optimize the organism’s chances of survival. Although the stress response is beneficial when acute, it may become detrimental to many aspects of health when repeated or chronic, or when the response is triggered after exposure to emotional stressors. For example, exposure to severe acute or chronic stressors can increase the risk of developing cardiovascular disease, disturb immune function, produce endocrine abnormalities and disrupt sleep architecture and diurnal/circadian physiological rhythms. Finally, disruptions in normal physiological rhythms may etiologically contribute to stress-related psychiatric disorders. The following set of pre-clinical studies sought to further our understanding of stress physiology using real-time biotelemetric assessments of several physiological parameters during exposure to different types of stressors. Specifically, these studies investigated the impact of stressor chronicity, stressor controllability and the stress-protective effects of regular voluntary physical activity on stress physiology. Results from the first experiment suggest that exposure to chronic repeated conditioned fear stress can produce outcomes consistent with those observed in post-traumatic stress disorder (PTSD) and that diurnal rhythm disruptions during repeated conditioned fear can predict sensitized physiological stress responses following subsequent exposure to an acute stressor. Results from the second experiment suggest that a relationship exists between stressor controllability and the heart rate response following stress exposure, but that acute stress-induced disruptions in diurnal physiological rhythms likely contribute little to the acute behavioral and affective consequences of stress that are sensitive to stressor controllability. The results from the third study suggest that prior physical activity leads to 1) an overall higher core body temperature and time spent in REM sleep and 2) facilitates the recovery of the normal diurnal REM sleep cycle following stress exposure. Both of these observed effects could contribute to the cognitive, affective and stress-protective benefits of exercise.

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