S. Rodríguez-Rosado, M. Cáceres-Chacón, A. Figueroa-Pérez, H. Haddock-Martínez,
G. Hernández-Busot, M. Rivera-López, O. Martínez-Guzmán, D. Sierra-Mercado
Dept. of Anatomy and Neurobiology., University of Puerto Rico School of Medicine, San Juan, PR
Glyphosate-based herbicides (GBH) are the most commonly used herbicides worldwide.
Glyphosate was initially considered safe for mammals because it acts by inhibiting a metabolic route not present in mammals. Recent studies have correlated an increase in the diagnosis of anxiety with the increased use of glyphosate. Studies in rodents have shown that large doses of glyphosate increase anxiety-like behaviors. Glyphosate exposure is regulated by the Environmental Protection Agency, which has established a chronic reference dose for glyphosate of 2.0mg/kg daily. Interestingly, the effects of this dose of glyphosate on anxiety has not been explored. Therefore, we aimed to evaluate the effect of prolonged consumption of GBHcontaminated drinking water on anxiety-like behaviors. To achieve this, rats were given access to glyphosate-contaminated drinking water ad libitum. Water was prepared with the required concentration of glyphosate to obtain a target dose of 2.0mg/kg daily. Control rats received filtered drinking water. After 4 weeks of exposure to GBH, we assessed for anxiety-like behavior using the open field test. No difference was observed in neither the amount of time spent in the center (GBH: 47.68; control: 49.01; p = 0.9051,), nor the number of entries into the center (GBH: 17.62; control: 17.33; p=0.9463). Moreover, after 10 weeks of exposure to GBH, anxiety-like behavior was reassessed in the elevated plus maze. Here, consumption of GBH resulted in a decrease in the time spent in the open arms (GBH: 45.36; control: 103.7; p=0.0086), as well as a decrease in the number of entries into the open arms (GBH: 4.39; control: 9.50, p=0.0214). Lastly, after a total of 14 weeks of exposure to GBH consumption, we assessed anxiety-like behaviors using the light/dark box. Similar to our previous observations, GBH reduced the percent of time spent in the light (GBH: 3.32; control: 13.03; p = 0.0173). Together, these results indicate that prolonged exposure to glyphosate at low doses increases anxiety-like behavior. Future directions include assessing other emotional memories such as fear conditioning, and performing immunohistochemistry on brain regions involved in anxiety-like behaviors such as the basolateral amygdala and bed nucleus of the stria terminalis.