PS3-12. Gestational and Lactational Exposure to Atrazine Depletes Dopamine Neurons in the Ventral Tegmental Area of Neonatal Boars.

Abstract Atrazine is a widely used herbicide for controlling weeds in the United States. Atrazine contamination in groundwater of agricultural states exceeds the Environmental Protection Agency limit (3 ug/L). Developing boars may be exposed to atrazine through maternal feed and drinking water. The herbicide is reported to interfere with the nigrostriatal dopamine system. However, little is known about its effect on the mesolimbic reward system. The aim of this study is to determine the effect of in utero exposure to environmentally relevant concentrations of atrazine on the mesolimbic dopamine neurons in the ventral tegmental area (VTA) of neonatal boars. Pregnant littermate sows drank water containing either vehicle [0.002 (v/v) ethanol; n = 3] or atrazine (20 ug/L; n = 4) ad libitum from gestation through parturition to lactation (98 days). The boars were humanely sacrificed, and their brains harvested 10 days post-natal. The VTA was processed for further analysis. Immunofluorescence for Tyrosine hydroxylase (TH) was performed as indirect assessment of dopamine neurons. Fluorescence images were obtained by confocal microscopy, and TH-positive neurons and relative fluorescence intensity quantified by ImageJ. Gene expression levels of TH, dopamine transporter (DAT) and Nurr1 were quantified by RT-qPCR. Three samples from each mother (control; n = 9; atrazine exposed; n = 12) were randomly selected for analysis. Differences were determined using Student t-test. The number of TH-positive neurons and relative fluorescence intensity in the atrazine exposed samples were significantly lower than the control group (P = 0.02 and P = 0.0003 respectively). No difference in total neuronal count was observed (P > 0.05). No differences in gene expression of TH, DAT and Nurr1 were detected (P > 0.05). In utero exposure to atrazine resulted in depletion of tyrosine hydroxylase positive neurons in the VTA of neonatal boars. This may disrupt homeostasis of the dopaminergic reward pathway and possibly interfere with sexual behavior of farm animals.