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Atrazine (ATR) is an herbicide broadly used in the world to control weeds in corn and sorghum fields, and it is potentially toxic for the dopaminergic system. Alterations in dopaminergic markers after ATR administration in rats and C57BL/6 mice have been reported. Behaviorally, it has been observed that ATR exposure causes hypoactivity shortly after its administration. To understand how acute ATR administration induces hypoactivity, we set out to map the brain areas responsive to ATR using c-Fos as a marker of neuronal activity, and tyrosine hydroxylase (TH) as a marker of dopaminergic neurons. The levels of glutamate and gamma-aminobutyric acid (GABA) were measured using high performance liquid chromatography, and spontaneous locomotor activity was evaluated as well. Male Sprague-Dawley rats received a systemic injection of 1% methyl cellulose (vehicle) or 100mg ATR/kg body weight to evaluate locomotor activity immediately after injection, c-Fos and TH immunohistochemistry in forebrain, midbrain and hindbrain, or glutamate and GABA content in various brain areas 90min after injection. To assess the possible involvement of the GABAergic system on ATR effects we tested the effects of a GABA-B antagonist. We found statistically significant decreases in locomotor activity, which were partially reversed by the GABA-B antagonist, and increases in the number of c-Fos-positive cells in thalamus, central amygdala, subthalamic nucleus, superior colliculus, and substantia nigra, TH positive cells were not selectively activated by ATR. The acute administration of ATR did not affect GABA or glutamate tissue levels but significantly decreased locomotor activity. These results corroborate the hypoactivity-inducing effect of ATR, and show that non-dopaminergic cells respond to the acute administration of ATR. The activation of cell populations in the basal ganglia and their target nuclei may contribute to the acute behavioral effects of ATR., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The widespread use of atrazine (ATR) and its persistence in the environment have resulted in documented human exposure. Alterations in hypothalamic catecholamines have been suggested as the mechanistic basis of the toxicity of ATR to hormonal systems in females and the reproductive tract in males. Because multiple catecholamine systems are present in the brain, however, ATR could have far broader effects than are currently understood. Catecholaminergic systems such as the two major long-length dopaminergic tracts of the central nervous system play key roles in mediating a wide array of critical behavioral functions. In this study we examined the hypothesis that ATR would adversely affect these brain dopaminergic systems. Male rats chronically exposed to 5 or 10 mg/kg ATR in the diet for 6 months exhibited persistent hyperactivity and altered behavioral responsivity to amphetamine. Moreover, when measured 2 weeks after the end of exposure, the levels of various monoamines and the numbers of tyrosine hydroxylase-positive (TH+) and -negative (TH-) cells measured using unbiased stereology were reduced in both dopaminergic tracts. Acute exposures to 100 or 200 mg/kg ATR given intraperitoneally to evaluate potential mechanisms reduced both basal and potassium-evoked striatal dopamine release. Collectively, these studies demonstrate that ATR can produce neurotoxicity in dopaminergic systems that are critical to the mediation of movement as well as cognition and executive function. Therefore, ATR may be an environmental risk factor contributing to dopaminergic system disorders, underscoring the need for further investigation of its mechanism(s) of action and corresponding assessment of its associated human health risks.