Subacute exposure of male rats to high concentrations (2000 ppm) of xylene, ortho-xylene, meta-xylene, para-xylene, and ethylbenzene produced discrete increases of dopamine and noradrenaline levels and turnover in various parts of the hypothalamus and the median eminence 16-18 hr following the last exposure to the aromatic hydrocarbons. Some of the above solvents also reduced the secretion of prolactin, corticosterone, and thyroid-stimulating hormone. Within the forebrain, only xylene produced increases of dopamine levels in various parts of the striatum and the subcortical limbic forebrain. Furthermore, only xylene itself produced widespread increases of dopamine turnover within the neostriatum and the subcortical limbic forebrain, while ethylbenzene selectively increased dopamine turnover within the dopamine-cholecystokinin-8 immunoreactive nerve terminals of the nucleus accumbens (posterior part). In contrast ortho-xylene produced widespread reductions of dopamine turnover in the above-mentioned areas. It is suggested that the changes discovered in dopamine and noradrenaline levels and turnover can produce disturbances in catecholamine neurotransmission in the brain leading to disturbed brain function, e.g., in neuroendocrine, mental, and motor control.
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