Effect of styrene on monoamine oxidase B activity in rat brain

Previous studies have indicated that workers exposed to styrene present a d ecreased activity of platelet monoamine oxidase B (MAO B), suggesting that this biochemical assay may represent a biomarker for styrene-induced neurot oxicity. This study was undertaken to determine whether exposure to styrene would cause changes in MAO B activity in the target organ-the brain. Group s of rats were exposed to styrene by inhalation at concentrations of 300 pp m for 4 wk or 50 ppm for 13 wk. Both treatments caused significant decrease s of MAO B activity in several brain areas, while MAO A activity war; not a ffected. Decreases in MAO B activity were also found in brainstem of rats g iven styrene (400 mg/kg) or styrene oxide (100 mg/kg) by ip injection for 2 wk. Styrene, styrene oxide, and other styrene metabolites (mandelic acid, phenylglyoxylic acid, and styrene glycol) had no direct inhibitory effect o n brain MAO B activity when tested in vitro. These results indicate that ex posure to low concentrations of styrene alters MAO B activity in rat brain, suggesting that the observed changes in human platelets may reflect altera tions in the nervous system.