Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Environmental Toxicology

Committee Member

Dr. Stephen Klaine, Committee Chair

Committee Member

Dr. Cindy Lee

Committee Member

Dr. Joseph Bisesi


A majority of American adults in today’s society are treated for anxiety with anti-anxiety medications. Some of these prescribed drugs are neither efficiently metabolized by the human body nor removed by wastewater treatment plants before they reach streams and rivers and so are often detected in the aquatic environment in trace concentrations. Once present in surface waters, they have the potential to cause adverse effects for aquatic organisms, including changes in both behavior and brain chemistry. Previous work has shown that upon exposure to 150µg/L fluoxetine, a selective serotonin reuptake inhibitor antidepressant, hybrid striped bass (M. saxatilis x M. chrysops) brain serotonin levels decreased by almost 50% over six days. This previous study also correlated reduced brain serotonin levels with behavioral alterations that decreased an organism’s ecological fitness, specifically the ability of the organism to capture its prey. Similarly, other studies have suggested that fluoxetine, along with other anti-anxiety medications, including diazepam and buspirone, has the ability to alter an organism’s anxiety behaviors. However, these studies failed to correlate the alteration in behavior with changes in brain neurotransmitter levels. While anxiety medications are designed to alter brain neurotransmitter levels, other investigators have suggested that other contaminants such as metals can also affect brain chemistry. A previous study has shown that carp exposed to sub-lethal levels of copper over the course of one week experienced decreased brain serotonin levels in three different parts of the brain. The current study characterized the effects of ethanol (positive control), fluoxetine, diazepam, buspirone, and copper exposure on brain chemistry and behavior in the fathead minnow (Pimephales promelas) using the standard light-dark anxiety behavioral bioassay. At the onset of the experiment, minnows exposed to ethanol, fluoxetine, and copper for one day displayed anxiolytic behaviors at lower concentrations. Longer exposures to buspirone and diazepam also elicited anxiolytic behaviors. Significant decreases in neurotransmitter levels were seen after exposure to ethanol, diazepam, and copper. In addition, my study further elucidated the relationship between brain chemistry and anxiety behaviors in fish, specifically the relationship between brain chemistry and minnow anxiety behavior after exposure to diazepam



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