The Impact of Dexamethasone on Behavioral Development in Larval Zebrafish (Danio rerio)

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Stress can have damaging effects on a developing organism. Cortisol, a glucocorticoid critical to the stress response, can readily permeate across the placental barrier, which may have long-lasting, deleterious effects on the stress response of the developing organism. The synthetic homologue of cortisol is dexamethasone (dex), a corticosteroid used as an anti-inflammatory drug in humans to treat various autoimmune diseases and cancer. Dex is also often given to preterm infants to accelerate fetal lung development prior to delivery. Research with animal models has linked prenatal dex exposure to increased fear reactivity, decreased loco motor activity, and elevated cortisol levels in response to stress, in addition to brain cell loss and neurodevelopmental disability. The present study used larval zebrafish (Danio Rerio) to examine the effects of dex exposure on anxiety-related behavior during a window critical for the devleopment of the Hypothalamic-Pituitary-Interrenal axis, a network of brain structures responsible for maintaining and facilitating negative feedback of the stress response. By varying exposure to dex (dex vs. control) and timing of exposure (0 to 12 hours vs 12 to 24 hours post fertilization), and examining the effect on motor behaviors in 5 day old zebrafish larvae, this study sought to advance our understanding of the mechanism by which prenatal stress may cause long-term changes in stress reactivity. Results did not support our hypotheses. There was no evidence of an effect for drug exposure or timing of exposure. There was, however, an unexpected interaction, such that larvae in the control condition presented the greatest changes in thigmotaxic behavior following the presentation of a novel stimulus.



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