From Genes to Organs: A Multi-Level Neurotoxicity Assessment Following Dietary Exposure to Glyphosate and Its Metabolite Aminomethylphosphonic Acid in Common Carp (Cyprinus carpio)

Herbicide glyphosate and its main metabolite, aminomethylphosphonic acid (AMPA), have raised concerns due to their potential neurotoxicity in non-target aquatic species. This study evaluated neurotoxic effects in common carp (Cyprinus carpio) following a 28-day dietary exposure to glyphosate (325.2 and 3310.0 μg/kg) and AMPA (335.2 and 3441.0 μg/kg) at two concentrations, including control and four treatment groups. Brain acetylcholinesterase activity was significantly (p < 0.05) reduced in all exposed groups, while muscle acetylcholinesterase activity remained unchanged. Brain dopamine was significantly (p < 0.05) decreased only in the highest AMPA group. Plasma butyrylcholinesterase activity increased significantly (p < 0.05) in the low-dose glyphosate group. The level of mRNA expression of ache was significantly (p < 0.05) downregulated in the brain across all treatments and upregulated in the gills only at the highest AMPA concentration. Histological analysis of the brain revealed vascular congestion in both glyphosate-exposed groups, indicating pathological changes. These results suggest that dietary exposure to glyphosate and AMPA can affect cholinergic and dopaminergic pathways in fish, with the brain being a particularly sensitive target tissue. Our findings contribute to understanding the potential neurotoxic risks posed by glyphosate-based compounds in aquatic environments.