Anxiety affects approximately 1/3 of the US population and presents in many different forms, ranging from social to panic disorders. It also presents with high comorbidity for other mental disorders. One treatment is Selective Serotonin Reuptake Inhibitors (SSRIs) which allow for increased activation of serotonin (5-HT) receptors. SSRIs come with an extensive list of side effects, which can fail to maintain quality of life. Cannabidiol (CBD) is a cannabis derived compound which has been shown to decrease anxiety by activation of multiple subtype 5-HT amine receptors. CBD has few side effects, is not psychoactive, and exhibits anti-psychotic properties. The current understanding of CBD\u27s mechanisms is limited specifically in invertebrates, where to date limited published research involves behavior and cannabinoids. Decapod crustaceans, such as crayfish, have emerged as a novel approach to studying drugs of abuse. Within the neural structures of the crayfish tails are 5-HT receptors that control tail-flips, a withdraw reflex when placed into a fight. Serotonin has also been linked to aggression and decision making for engaging in fights with other crayfish. Additionally, evidence currently suggests CB1 receptors are present at neuromuscular junctions (NMJ) and may have an impact on motility. For this thesis, crayfish were administered either CBD, 5-HT, or a vehicle control. Analysis of motility by percent of time moving or rest, amount of food consumed, and aggression in paired fights were conducted. No statistical significance was found for CBD influencing motility and hunger. However, the duration of fights significantly increased when injected with CBD and when paired with 5-HT injected crayfish. This evidence supports the main hypothesis that CBD increases serotonin receptor activity in crayfish as seen with SSRIs, thus could be of use in treating anxiety
