Glyphosate exposure induces synaptic impairment in hippocampal neurons and cognitive deficits in developing rats

Abstract

Glyphosate is the active ingredient of several widely used herbicide formulations. Studies based on Glyphosate exposure in diferent experimental models have suggested that the nervous system represented a key target for its toxicity. Previously, we demonstrated that exposure to glyphosate during gestation induces defcits on behavioral and cognitive function in rats. The aim of the present work was to examine whether cognitive dysfunction induced by Glyphosate was connected to changes on synapse formation and maturation. To understand how glyphosate afects synaptic assembly, we performed in vitro assays on cultured hippocampal neurons that were exposed to the herbicide (0.5 or 1 mg/mL) for 5 or 10 days. Biochemical and immunocytochemical approaches revealed that Glyphosate treated neurons showed a decrease on dendritic complexity and synaptic spine formation and maturation. Moreover, results indicated that Glyphosate decreased synapse formation in hippocampal neurons. To evaluate these efects in vivo, pup rats were treated with 35 or 70 mg/kg of Glyphosate from PND 7 to PND 27, every 48 h. Results indicated that Glyphosate postnatal exposure induced cognitive impairments, since recognition and spatial memory were altered. To go further, we evaluated synaptic protein expression and synaptic organization in hippocampus. Images revealed that Glyphosate treatment downregulates synapsin-1, PSD-95, and CaMKII expression, and also decreased PSD-95 clustering in hippocampus. Taken together, these fndings demonstrate for the frst time that Glyphosate exposure afects synaptic assembly and reduced synaptic protein expression in hippocampus and that likely triggers the impairment of cognitive function and neuronal connectivity.