Date of Award

Winter 12-5-2020

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Major Professor

Dr. Lisa Ganser

First Committee Member

Dr. Thomas McElroy

Second Committee Member

Dr. Martin Hudson

Abstract

Stress is a state of threatened homeostasis counteracted by various physiologic and behavioral responses aimed to maintain or restore balance. As such, stress acts as a motivator to perform during the challenges of life to survive. Chronic perturbations to the stress response homeostasis without relief can lead to dysregulation, thus attenuating organ systems and structures and causing significant damage {1]. Individuals who undergo psychological trauma endure an acute and transient experience, which results in minimal functional impairment, but some suffer from a chronic condition called posttraumatic stress disorder (PTSD). Individuals who have PTSD are likely to experience intense stress, fear, anxiety, and helplessness, resulting in a permanent or temporary psychological wound characterized by physical, cognitive, emotional, or behavioral changes. In this study, we will be exploring the physiologic and behavioral effects of chronic stress on functionally distinct brain areas related to reward and aversion, the neuromodulator dopamine (DA), and DA’s critical role in mediating behaviors used to meet survival needs.

In this study, we used the zebrafish to model PSTD by implementing a chronic unpredictable stress paradigm to simulate a traumatic experience. We measured behavior differences using an anxiety-like behavior assay, the Light-Dark Preference Test, and attempted to validate our findings using immunohistochemistry and microscopy to observe brain changes in regions of interest involving aversion. Though experimental zebrafish did respond to stressful stimuli, exhibiting typical anxiety-like behaviors, there was no significant difference amongst our groups. Multiple behaviors were present but unquantifiable due to experimental error. Additionally, we found there to be no significant difference in the effect of PTSD on the brain. However, post ad-hoc tests indicated individual differences amongst experimental groups for the average time in the light compartment statistic, the number of crosses into the light compartment statistic, and the single pairwise difference in tyrosine hydroxylase (TH) expression, suggesting that stress still may induce anxiety behaviors and affect the neurocircuits that modulate stress. These outliers prompt additional trials with larger sample sizes.

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