Developmental neurotoxicity of atrazine: decreased synaptic spine density and miRNA-driven GluN2A downregulation in primary hippocampal neurons.

Atrazine (ATZ) is a triazine herbicide and a persistent environmental contaminant. Its use is associated with effects on the nervous system in experimental models. Behavioral and molecular alterations have been reported after exposure, but the cellular mechanisms underlying atrazine-induced developmental neurotoxicity remain unclear, particularly at the synaptic level. In this study, we investigated the effects of ATZ exposure on glutamatergic synaptic maturation in rat primary hippocampal neurons. Neuronal cultures were exposed to ATZ throughout the in vitro developmental period, and structural and molecular endpoints were assessed. Dendritic spines were analyzed by confocal microscopy, and the expression of glutamatergic receptor subunits was evaluated by Western blot and RT-qPCR. In parallel, microRNA expression profiles targeting NMDA receptor subunits were examined to explore post-transcriptional regulatory mechanisms. ATZ exposure induced a selective reduction in dendritic spine density, without detectable changes in spine morphology. This structural effect was accompanied by a selective decrease in the NMDA receptor subunit GluN2A at both protein and mRNA levels, while GluN1, GluN2B, and AMPA receptor subunits were unaffected. Notably, GluN2A downregulation was preceded by the upregulation of microRNAs predicted to target the GRIN2A transcript, indicating a microRNA-mediated regulatory mechanism. Overall, these results demonstrate that ATZ can interfere with hippocampal synaptic maturation by selectively modulating NMDA receptor subunit composition through epigenetic mechanisms. This study identifies dendritic spine and GluN2A regulation as sensitive endpoints of ATZ-induced developmental neurotoxicity and provides mechanistic insight into how early synaptic processes may be affected by this herbicide.