Date of Award

January 2021

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Lisa S. Middleton

Department Affiliation

Biological Sciences

Second Advisor

Tanea T. Reed

Department Affiliation

Chemistry

Third Advisor

Lindsay E. Cormier (Calderon)

Department Affiliation

Biological Sciences

Abstract

Cannabidiol (CBD) is the second most abundant cannabinoid found in Cannabis sativa and its array of therapeutic effects make it a popular target of pharmacological research. Though its properties are psychoactive in nature, abuse and dependence of CBD has never been reported. Its beneficial side effects are mediated through the endocannabinoid system (ECS), as it functions as an antagonist at cannabinoid receptor 1 (CB1). However, recent evidence suggests that CBD may also be a CB1 negative allosteric modulator of (−)-trans-Δ9-tetrahydrocannabinol (Δ9-THC). Interestingly, the ECS is linked to the main circuit thought to modulate reward signaling when taking substances of abuse, the dopamine (DA) pathway. The DA pathway contains dopaminergic cell bodies originating in the ventral tegmental area (VTA), where reward-related information is carried to the nucleus accumbens (Acb). CB1 receptors are shown densely located across these regions, causing speculation as to the role of the ECS in reward functioning. In addition to these two systems interacting, one study found that CBD acts as a partial agonist at dopamine D2 receptors. Although experiments have shown CBD and its behavior at CB1 and D2 receptors, no studies exhibit what CBD does at the receptor-level when given in combination with CB1 and D2 receptor agonists during acute or chronic treatment. Therefore, the objective of this thesis was to examine the effect CBD has on signaling alone and in combination with CB1 and D2 receptor agonists at 5-minutes (acute) and 21-hours (chronic). SH-SY5Y cells were used as the model due to the native presence of both CB1 and D2 receptors. Western blot analyses were performed by probing protein samples for CB1 and D2 receptors and quantifying protein concentrations for each treatment. Confocal microscopy was utilized to show CB1 and D2 receptor localization. Lastly, cAMP assays were run to measure levels of cAMP production during each drug treatment since levels have been shown to increase at the D2 receptor but decrease at the CB1 receptor. From representative Western blot analyses, acute treatments did not appear to alter CB1 or D2 receptor concentrations. However, for chronic treatments, CB1 receptor concentration seemed to be changed at treatment groups: WIN + QUIN, WIN + CBD, WIN + CBD + QUIN, and QUIN + CBD. No apparent alterations were seen for D2 receptor concentration levels for chronic treatments. Preliminary data obtained from confocal microscopy and cAMP assays will need to be further examined and compared before results can be deemed significant. Overall, by understanding CBD and its functioning at the CB1 and D2 receptors, future clinical treatment paradigms can be better informed.

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