Isabel Castro-Rivera, Marcel González-Pedraza, Alexdiel Figueroa Perez, Héctor G. Haddock-Martínez, Héctor A.

Haddock Martínez, Gabriela Hernández-Busot, Melissa Rivera-López, Mauricio Cáceres-Chacón, Osmarie

Martínez-Guzmán, and Demetrio Sierra-Mercado

Department of Anatomy & Neurobiology, University of Puerto Rico School of Medicine


Glyphosate is the active ingredient in several commercial herbicides. Though initially considered safe for mammals, recent reports suggest that glyphosate administration at unusually high doses increases anxiety-like behaviors. However, few studies have evaluated the neurobehavioral effect of glyphosate exposure at the low concentration levels that the Environmental Protection Agency considers safe for human consumption. Grooming behavior , one of the most frequently performed behaviors in rodents, has been proposed as a measurement for states of generalized anxiety.

Thus, we hypothesized that prolonged exposure to levels of glyphosate thought to be safe for humans will increase general anxiety-like behavior observed as abnormal grooming behavior in rats. To test this hypothesis, male Sprague Dawley Rats (n=13) had access ad libitum to drinking water containing glyphosate at a dose of glyphosate considered safe (2.0mg/kg) for 16 weeks, whereas control rats received filtered drinking water. After glyphosate exposure, rats were recorded in their home cage for 5 minutes. Videos were scored for total time spent grooming, as well as distance traveled and time where the rat was immobile. Preliminary data shows that glyphosate exposure does not affect the total number of grooming bouts (glyphosate: 0.67, control: 3.50; p=0.1268). Interestingly, however, glyphosate exposure decreased total distance traveled (glyphosate: 9.73, control: 15.79; p=0.0318) and increased the total time immobile (glyphosate: 429.30, control: 329.10; p=0.0364. Future directions include assessing the brain tissue for changes in biomarkers of neuronal activity in the central amygdala , a brain region implicated in anxietylike behaviors. The results of this study will allow us to elucidate the potential neurotoxic effects that glyphosate consumption may have on the brain, and how these effects could manifest as behaviors in rats.

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