Characterization of seizures induced by acute exposure to an organophosphate herbicide, glufosinate-ammonium

Glufosinate-ammonium (GLA), the active component of a widely used herbicide, induces convulsions in rodents and humans. In mouse, intraperitoneal treatment with 75mg/kg GLA generates repetitive tonic-clonic seizures associated with 100% mortality within 72h after treatment. In this context, we characterized GLA-induced seizures, their histological consequences and the effectiveness of diazepam treatment. Epileptic discharges on electroencephalographic recordings appeared simultaneously in the hippocampus and the cerebral cortex. Diazepam treatment at 6h immediately stopped the seizures and prevented animal death. However, intermittent seizures were recorded on electroencephalogram from 6h after diazepam treatment until 24h, but had disappeared after 15 days. In our model, neuronal activation (c-Fos immunohistochemistry) was observed 6h after GLA exposure in the dentate gyrus, CA1, CA3, amygdala, piriform and entorhinal cortices, indicating the activation of the limbic system. In these structures, Fluoro-Jade C and Cresyl violet staining did not show neuronal suffering. However, astroglial activation was clearly observed at 24h and 15 days after GLA treatment in the amygdala, piriform and entorhinal cortices by PCR quantitative, western blot and immunohistochemistry. Concomitantly, glutamine synthetase mRNA expression (PCR quantitative), protein expression (western blot) and enzymatic activity were upregulated. In conclusion, our study suggests that GLA-induced seizures: (a) involved limbic structures and (b) induced astrocytosis without neuronal degeneration as an evidence of a reactive astrocyte beneficial effect for neuronal protection. Copyright (C) 2016 Wolters Kluwer Health, Inc. All rights reserved.