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THE EFFECT OF CANNABINOIDS ON THE DEVELOPMENTAL MORPHOLOGY OF ZEBRAFISH**

Abstract

Prior results on exposure of zebrafish embryos to both Δ9-THC and Δ8-THC demonstrated delayed hatch rate, higher death rate and shorter embryos with curved spines when compared to control embryos. In this study, we also examined the effects of cannabidiol (CBD), a widely available, legal substance used as treatment for numerous ailments from relieving pain or stress to enhancing sleep. We compared the effects of treatment with CBD, Δ8-THC, and Δ9-THC to experimental controls on the embryonic development of zebrafish, Danio rerio. Embryos were randomly divided into groups receiving 0, 0.15, 0.3, 0.6, 1.25, 2.5 and 5 µg/ml of each of these cannabinoids. We monitored embryos daily to record the number of embryos that were dead or alive. We also recorded daily how many had hatched from their chorions. Embryos were allowed to develop until day four post-fertilization (4 dpf) when spinal curvature and heart rates were assessed. We then anesthetized the embryos, fixed them in 4% paraformaldehyde overnight and stored them in 100% methanol at 20° C for morphologic assessment of jaw structure using Alcian blue staining of cartilage and to examine the pattern of neural development through immunofluorescent staining. This project is ongoing, and we have yet to examine jaw structure or neural development. Initial data suggest that CBD, like Δ8-THC and Δ9-THC, promotes spinal curvature, mortality, delayed hatch rate, and decreased heart rates. Thus, exposure to CBD, like Δ9-THC and Δ8-THC, does not appear to be safe during embryo development. While we cannot extrapolate the results of this study to humans, caution may be appropriate, given the high conservation of genetics and key signaling pathways between humans and zebrafish, a model being increasingly used for developmental studies.

Acknowledgements

Young Harris College QEP

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