Relationship of Essential Oil Exposure to Anxiety in Zebrafish

Abstract

This study focused on the relationship between differing essential oils and their impact on zebrafish anxiety. Five test groups were used to observe the behavioral responses and measure the quantitative cortisol levels of the fish after being exposed to three different essential oils, a carrier oil, and a control group (no oil). Two separate tests were designed to study 20 zebrafish over the course of 7 weeks. First, the swimming behaviors of the fish were observed using a basic novel tank test (NTT). The swimming patterns of the fish were recorded and the percent time that each fish swam in the top half of the tank was compared to the time each fish swam in the bottom half of the tank. Second, the zebrafish blood cortisol concentrations were measured immediately following their exposure to the differing test treatments using a cortisol extraction ELISA kit. The two data sets supported a strong trend regarding essential oil types in relation to swimming patterns and cortisol concentrations. Both data sets agreed that the test groups exposed to lavender, coriander, and fractionated coconut oil exhibited less anxious swimming behavior and lower levels of cortisol, while the zebrafish exposed to lemongrass oil and only water showed increased anxious behavior and higher levels of cortisol. Both tests showed strong trends when analyzed with a one‐way ANOVA test. The novel tank test data set had a p‐value of 0.07 and the cortisol extraction test had a p‐value of 0.06. The results of this study show that many questions can still be asked and answered regarding essential oil effects on cortisol levels and stress responses in zebrafish.