Term of Award

Summer 2016

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Department

Department of Biology

Committee Chair

Johanne Lewis

Committee Member 1

Vinoth Sittaramane

Committee Member 2

Christine Bedore

Abstract

Vertebrate sleep is a universal phenomenon and encompasses an array of conserved behavioral and physiological characteristics. Studies of sleep in humans have shown that sleep deprivation leads to adverse effects to human health and additional stress. Teleosts have emerged as a useful model species to study the vertebrate stress response, given its stress axis has high levels of homology with the mammals, including humans. For this study, the behavior of zebrafish (Danio rerio) subjected to acute (24 hours) and chronic (20 days) extended light exposure was monitored and whole-body cortisol was analyzed as an indication of activation of the vertebrate stress response. Additionally, transcriptome responses of key genes in the biosynthetic pathway of cortisol (P450scc and 11b-hyd) were analyzed with qRT-PCR to investigate the effects of sleep deprivation at the molecular level. We hypothesized that sleep-deprived zebrafish would display increased levels of activity, suggesting lack of “sleep-like” state, which would lead to higher stress, subsequent cortisol production and upregulation of P450scc and 11b-hyd expression when compared to control fish. Zebrafish were found to significantly increase activity during extended light exposures, suggesting a disturbance of sleep/wake behavioral cycles. Interestingly, the behavioral changes were not accompanied with a significant increase in whole-body cortisol in response to acute or chronic extended light exposure. At the transcriptome level, P450scc was significantly upregulated 13.23-fold in the acute sleep deprivation trial, but no significant changes in expression were observed in the chronic trial. There were no changes in 11b-hyd expression levels found in either extended light treatments. In conclusion, acute and chronic extended light exposure resulted in increased activity throughout subjective night hours, but this behavioral change was not accompanied by an increase in whole-body cortisol concentrations, suggesting that lack of sleep-like state does not result in stress in zebrafish. An upregulation of P450scc in the acute extended light exposure suggests cholesterol was being cleaved to be readily available for cortisol production if it was later needed, or to possibly become precursors to sex hormones in order to aid in aggressive behavior.

Research Data and Supplementary Material

No

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