Behavioral effects of subchronic inorganic manganese exposure in rats

Background: Manganese, an essential micronutrient, is a potential neurotoxicant in prolonged overexposure. Parkinson- like syndrome, motor deficit, disturbed psychomotor development are typical signs of neuropathological alterations due to Mn in humans. Methods: Young adult rats, in three groups of 16 each, received 15 and 59 mg/kg b.w. MnCl2, (control: distilled water) via gavage for 10 weeks, and were kept for further 12 weeks. Correlation of MnCl2 exposure to body and organ weights, neurobehavioral effects (spatial memory, exploratory activity, psychomotor performance, pre-pulse inhibition), and histopathological changes (gliosis) was sought. Results: By the end of treatment, Mn accumulated in blood, cortex, hippocampus, and parenchymal tissues. Body and organ weights were reduced in high dose rats. All treated rats showed hypoactivity, decreased memory performance, and diminished sensorimotor reaction. In the dentate gyrus of these, GFAP immunoreactivity increased. During the post-treatment period, body weight of the high dose group remained decreased, locomotor activity returned to control, but the lasting effect of MnCl2 could be revealed by amphetamine. Conclusion: Using complex methodology, new data were obtained regarding the relationship between the long-term effects of MnCl2 at neuronal and behavioral level. Š 2007 Wiley-Liss, Inc