Cortisol is a hormone released in response to stress that is also vital to human development. Previous studies in lab have shown that cortisol exposure of zebrafish embryos resulted in hypolocomotion with increasing cortisol concentration. Cortisol acts through two receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). We tested if the activation of the GR receptor would produce similar effects on behavior to cortisol exposure. Dexamethasone is a synthetic gluccocorticoid that selectively binds to the GR. Zebrafish embryos were collected and treated with different concentrations of dexamethasone at 4-6 hours post-fertilization (hpf) in a 12-well plate. The resulting zebrafish were transferred at 5dpf to a 96-well plate, which was then measured in an 18-minute alternating light-dark assay to assess their locomotor behavior using a commercial motor tracking system. Two rounds of experiments, consisting of concentrations ranging from 100 to 1 uM showed differential relative behavioral phenotypes at different concentrations. These experiments inform our understanding of how corticosteroid receptors affect zebrafish behavior in embryonic development.
