Date of Award

Summer 7-22-2020

Degree Type


Degree Name

Master of Science in Integrative Biology (MSIB)



Committee Chair/First Advisor

Thomas McElroy

Major Professor

Lisa Ganser

Second Committee Member

Joel McNeal

Third Committee Member

Christopher Cornelison


This thesis is dedication to Faye Annette Goffigan, my forever angel.


The heavily conserved neural circuits that govern the vertebrate reward system, receive sensory stimuli and produce appropriate, self-preserving responses that correspond to experience-based learning and are driven by the communication of dopamine. Many of these circuits lie within the endocannabinoid system (ECS). At the most basic level, the ECS drives homeostatic behaviors, such as seeking nutrients, avoiding danger, and reproductive function. Unfortunately, this system can be hijacked by psychoactive drugs which ultimately alter the expression of dopamine. Cannabis sativa has two main active ingredients, THC and CBD, which modify the ECS receptor’s ability to bind to hormones and neurotransmitters such as dopamine. The specific effects of CBD on a developing nervous system have rarely been studied. Zebrafish, a viable translational model for embryonic and neural development, is a cost-effective and translational model that has previously been used in drug research. In the present study, zebrafish embryos were chronically exposed to CBD for 10 days. Embryonic development was assessed at 24- and 48-hours post fertilization and later at 10 days post fertilization. CBD exposure did not significantly alter survival or hatch rate but did increase the prevalence of pericardial and yolk sac edema. Because CBD required a 0.05% ethanol vehicle to dissolve into the embryo water, the experimental outcomes involving CBD were also influenced by ethanol exposure. Furthermore, a large variance in tyrosine hydroxylase expression in diencephalic dopaminergic nuclei was observed with CBD exposure. These data suggest that early impairments potentially caused by chronic CBD exposure during embryonic development and changes in TH expression during a critical developmental period development may have varying effects on the establishment of neural circuits by 10 days post fertilization; however the long-term effects of this are still unknown.

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