The effects of paroxetine-induced transient apoptosis and brain remodeling on social behavior in developing zebrafish

Autism spectrum disorder (ASD) is a neurodevelopmental condition caused by various genetic and environmental factors. This disorder has the cardinal symptoms including impaired social behavior involving the amygdala. Antidepressants such as paroxetine in early pregnancy increase the risk of ASD in offspring. However, a comprehensive picture of the underlying pathogenic mechanisms remains elusive. Here, we demonstrate that early exposure of zebrafish embryos to paroxetine suppresses neurogenesis in the optic tectum and the dorsal telencephalon which corresponds to the human amygdala. Paroxetine-treated embryos exhibit impaired growth, with small heads and short body lengths resulting from transient apoptosis. This is reminiscent of the early-onset fetal growth restriction (FGR) associated with ASD. Interestingly, the suppressed neurogenesis in the small heads was found to be restored after the cessation of paroxetine. This was accompanied by extended retinotectal projections, suggesting brain-preferential remodeling. Finally, the paroxetine-treated fish exhibited impaired social behavior, further supporting the correspondence with ASD. Our findings offer new insights into the early neurodevelopmental etiology of ASD. ### Competing Interest Statement The authors have declared no competing interest.