Long-term impact of embryonic exposure to ethinylestradiol and clotrimazole on behavior and neuroplasticity in zebrafish (Danio rerio)

Estrogen receptors (ER) are widely expressed in the brain of many species and experimental results highlighted the role of estradiol in neuronal plasticity and behavior. Consequently, the brain is therefore a prime target for endocrine disrupting chemicals (EDCs) interacting with estrogen signaling. Very little is known about the late effects of early disruption of estrogen signaling by EDCs. We focused on: ethinylestradiol (EE2; ER agonist) and clotrimazole (inhibitor of key steroidogenesis enzymes, including aromatases). Zebrafish eleutheroembryos were exposed (0-5 days) and then raised normally until adulthood. Several behavioral tests were performed in adults, then cell proliferation and dopaminergic neurons were quantified in several brain regions using immunostaining. Overall, a developmental exposure to EDCs stimulates cell proliferation in the dorsal telencephalon. At environmentally-relevant concentrations, male fish exposed to EE2 exhibited increased activity levels and decreased social behavior, posing a potential risk to population balance and health.