Therapeutic vitamin A doses increase the levels of markers of oxidative insult in substantia nigra and decrease locomotory and exploratory activity in rats after acute and chronic supplementation.

Vitamin A is known to regulate some central nervous system (CNS)-associated functions. Vitamin A at high doses has been demonstrated to be beneficial in the treatment of some diseases, for instance acute promyelocytic leukemia. However, vitamin A and its naturally occurring metabolites (retinoids) are known to alter neuronal function, inducing behavioral disorders. Here we provide an evidence to indicate that vitamin A supplementation, at both therapeutic and excessive doses, induces oxidative stress in the rat substantia nigra. Vitamin A supplementation induced lipid peroxidation, protein carbonylation, and oxidation of protein thiol groups, as well as change in catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activity. Surprisingly, locomotory and exploratory activity of rats were decreased after acute and chronic vitamin A supplementation. Therefore, we may conclude from our results that vitamin A supplementation is prooxidant to the rat substantia nigra and effective in altering behavior.