Date of Award

Spring 2018

Project Type

Thesis

Program or Major

Psychology

Degree Name

Doctor of Philosophy

First Advisor

ROBERT C DRUGAN

Second Advisor

SERGIOS CHARNTIKOV

Third Advisor

THOMAS FOXALL

Abstract

When we are exposed to a traumatic or stressful life event, some individuals may develop symptoms of anxiety or depression while others may appear unaffected. In humans and nonhuman organisms, the ability to cope plays a large role in how an organism responds to a stressor, and this coping may be influenced by innate mechanisms. We have identified the use of ultrasonic vocalizations during intermittent swim stress (ISS) to forecast innate behavioral differences in stress reactivity. Vocalizing rats are resilient as they exhibit less cognitive impairment, motivational changes, and fewer anxiety-like behaviors typically observed post-ISS. Resilience should be associated with an active, stress buffering coping strategy during ISS, whereas non-vocalizing should exhibit more passive behaviors. These active or passive behaviors are driven by a corticolimbic serotonergic circuit originating in the dorsal raphe nucleus. Active coping is associated with reduced dorsal raphe serotonin activity, which leads to reduced post-stress impairment. We hypothesized vocalizing rats would engage in active coping responses, display fewer anxiety-like behaviors, and exhibit decreased serotonergic activation in the dorsal raphe nucleus compared with non-vocalizing rats. We found vocalizing rats exhibited reduced post-stress social anxiety, but engaged in passive coping during stress. Vocalizing rats further exhibited increased serotonergic activity in stress-responsive subregions of the dorsal raphe nucleus compared to non-vocalizing and unstressed controls. These data are the first to verify the coping strategy and associated serotonergic activity of vocalizing rats as a novel model of stress resilience.

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