Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. Peter van den Hurk, Committee Chair

Committee Member

Dr. Joseph H. Bisesi, Jr.

Committee Member

Dr. Thomas Schwedler

Abstract

Prescription drug use continues to increase across the United States. An important part of these medications are selective serotonin reuptake inhibitors (SSRIs) that function as anti-depressants and include drugs as citalopram (Celexa) and sertraline (Zoloft). SSRI's main mode of action is the inhibition of the serotonin reuptake transporter, causing a buildup of extracellular serotonin, one of the neurotransmitters in the central and peripheral nervous system. SSRIs can be considered persistent pollutants due to their continuous release from wastewater treatment effluent, drug manufacturing effluent, and agricultural runoff. Aquatic organisms can become non-target organisms when subjected to sub-lethal concentrations (low ppb to high ppm) of antidepressants. Behavioral tests provide sensitive endpoints for determining whether aquatic organisms have been subjected to antidepressants, causing changes in their ecological fitness. The goal of this research was to determine whether SSRIs cause sublethal effects in fish populations through a change in feeding behavior, supported by brain and plasma chemistry and changes in serotonin-related gene expression in the intestine. We hypothesized a decrease in feeding behavior, a decrease in serotonin levels, and a change in gene expression after exposure to sertraline and citalopram. Hybrid striped bass (HSB) exposed to citalopram (6-day exposure at 50-150 µg/l) and sertraline (4-100 µg/l, 6 days exposure, 6 days recovery) were fed every three days to determine effects on behavior. Blood, brain, and intestine samples collected from euthanized fish every three days were analyzed for concentrations of citalopram, sertraline, and serotonin. Both sertraline and citalopram caused a change in predatory behavior during exposure, with sertraline having a more dramatic effect than citalopram. The sertraline recovery period showed that the bass was able to rapidly return to normal feeding behavior, even while the antidepressant was still located in the brain and plasma. Citalopram and sertraline were both detected in brain and plasma samples, but in different levels during the exposure and recovery period. Serotonin levels also differed between each SSRI treatment. Our results showed that SSRIs may cause an upregulation of both the serotonin reuptake transporter and cholecystokinin, a satiation signaling protein. From an ecological standpoint, an increased feeding time could make exposed bass populations less ecologically fit compared to other populations that are not as affected by antidepressants.

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