Date of Award

Summer 8-6-2020

Degree Type

Thesis

Degree Name

MS Experimental Psychology

Department

Psychology

Advisor

Amy S. Hunter, Ph.D.

Committee Member

Michael Vigorito, Ph.D.

Committee Member

Marianne Lloyd, Ph.D.

Keywords

sex differences, REM sleep, PTSD, anxiety, depression

Abstract

Findings from both human and animal studies suggest rapid eye movement (REM) sleep disturbances following a traumatic event can lead to inability to extinguish the fear association, and eventually influence the development of post-traumatic stress disorder (PTSD). Additionally, research has demonstrated that sleep disruptions, including REM sleep deprivation (RSD), increases anxiety- and depressive-like behaviors and states in animals and people, with evidence of sex differences. Furthermore, it has yet to be determined whether short-term RSD, a more natural animal model of PTSD, can influence affective state of subjects. The present study applied short-term RSD to investigate sex differences in the relationship between sleep and anxiety- and depressive-like behaviors. Consistent with previous studies, short-term RSD was hypothesized to increase anxiety-like behaviors in the EZM in female subjects, in addition to significantly affecting depressive-like behaviors in both sexes in the FST and SPT. For 5 consecutive days, male and female rats were exposed to 6 hours of either RSD or control condition (8 male and 8 female per sleep condition) prior to a 2 hour SPT session. RSD was accomplished by utilizing the flowerpot method, which allowed subjects to undergo non-REM (NREM) sleep, but prevented them from entering REM sleep. On the final day of sleep manipulation, subjects were assessed in 5 minute trials using the elevated zero maze (EZM) and forced swim test (FST) following the sleep session. The dependent measures were start latency, head dips, stretch-attend postures, and percentage of time in closed areas for the EZM, as well as duration of and latency to immobility for the FST. In order to evaluate for delayed effects of RSD, the SPT continued for another 5 days, while sleep was undisturbed. Results revealed no effect of RSD on anxiety-like behaviors in the EZM or depressive-like behaviors in the FST. However, male rats displayed greater depressive behaviors in the FST than female subjects. Therefore, the first two hypotheses were not supported, since sleep condition did not affect anxiety- or depressive-like behaviors. However, male RSD rats exhibited immediate and delayed effects in the SPT, although these were transient-lasting, which partially supports the third hypothesis.

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