Early-life microplastic exposure elicits ADHD-like behaviors by disrupting dopaminergic neurodevelopment in zebrafish

Microplastics (MPs) are emerging environmental contaminants with potential neurodevelopmental risks. We investigated the effects of early-life exposure to polystyrene microplastics (PS-MPs; 0.1 μm and 5 μm) in zebrafish larvae (from 8 h post-fertilization to 5 days post-fertilization) across a range of concentrations (0, 0.1, 10, and 100 μg/mL). Larvae in most exposure groups exhibited ADHD-like behavioral phenotypes, characterized by increased locomotor activity and prolonged episodes of high-velocity movement bursts, indicative of hyperactivity and impulsivity. TH immunostaining showed a ∼30 % increase in dopaminergic neurons in larvae exposed to 0.1 μm PS-MPs (1 and 10 μg/mL) compared to controls.Transcriptomic analysis further identified dysregulation of multiple dopamine-associated signaling genes. Notably, pharmacological blockade of dopamine receptors ameliorated the behavioral abnormalities. These findings demonstrate that early-life exposure to PS-MPs can perturb dopaminergic neurodevelopment and elicit ADHD-like behaviors in zebrafish, highlighting microplastics as potential environmental risk factors for neurodevelopmental disorders during critical developmental windows.