Cortisol is a stress hormone that is vital to human development. Previous studies in the lab have found that embryonic exposure to cortisol alters morphological development in zebrafish. Cortisol primarily acts through two receptors, the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), which are crucial to the regulation and development of many physiological processes. Dexamethasone is a synthetic glucocorticoid that binds selectively to the GR. This study aimed to identify the lowest observable adverse effect limit (LOAEL) of exposure on embryonic zebrafish in order to better understand which developmental effects may be directly related to GR activation. Zebrafish embryos were exposed to various concentrations of dexamethasone between 3 and 72 hours post fertilization (hpf) and then imaged with a brightfield microscope to qualitatively evaluate any observable phenotypic abnormalities. Preliminary results showed morphological phenotypes increased as the concentration of dexamethasone increased. These data suggest that an excess of GR regulation results in developmental abnormalities. Additional experiments are needed to determine the LOAEL and confirm the results with statistical analyses. These experiments inform our understanding of how corticosteroid receptors affect zebrafish morphology in embryonic development.
