Subclinical effects of groundwater contaminants. II. Alteration of regional brain monoamine neurotransmitters by benzene in CD-1 mice

Abstract

Benzene, a common groundwater contaminant, possesses neurotoxic and behavioral effects. Male, adult CD-1 mice were continuously fed drinking waterad libitum containing 0, 31, 166 and 790 mg/L benzene for four weeks. Endogenous levels of the catecholamines norepinephrine (NE) and dopamine (DA), the catecholamine metabolites 3-methoxy-4-hydroxymandelic acid (VMA), 3,4-di-hydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the indoleamine serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), were measured by high-performance liquid chromatography (HPLC) in six discrete brain regions. In the hypothalamus, the brain region richest in NE, concentrations of NE increased by 40, 58 and 61% when mice received doses at 31, 166 and 790 mg/L, respectively. Significant increases of NE were also observed in the medulla oblongata and cerebellum. Dopamine concentrations increased significantly in the hypothalamus and corpus striatum. Increases of catecholamine metabolites were seen in a number of brain regions: midbrain (DOPAC), corpus striatum (VMA, DOPAC, HVA), cerebral cortex (VMA) and cerebellum (VMA). Benzene ingestion significantly increased 5-HT concentrations in the hypothalamus, corpus striatum, midbrain, cerebral cortex and medulla oblongata. Concomitant with increases of 5-HT, 5-HIAA increased in corpus striatum, midbrain, cerebral cortex and medulla oblongata. The findings indicate that oral ingestion of benzene by CD-1 mice induced both synthesis and catabolism of the monoamine neurotransmitters investigated.