High intake of folic acid attenuates 6-hydroxydopamine-induced Parkinsonism

High levels of homocysteine (Hcy) might accelerate dopaminergic cell death through oxidative stress and excitotoxicity. Folate plays an important role in the control of plasma levels of Hcy. In this study, effect of supplementation with folic acid on the 6-hydroxydopamine (6-OHDA)-induced Parkinsonism in rat and also serum level of Hcy was investigated. Rats were fed with folic acid supplements from 1 month before stereotaxic injection of 6-OHDA until to the end of experiments. 6-OHDA was injected into the striatum and development and severity of the Parkinsonism were assessed by conventional behavioral tests. Serum levels of Hcy before surgery and at the end of the behavioral tests were measured. Our results show that 10-fold supplementation, but not 2-fold supplementation of folic acid, significantly attenuates severity of 6-OHDA-induced Parkinsonism. 5-fold supplementation of folic acid also slightly decreased behavioral symptoms of Parkinsonism. Measurement of Hcy levels of sera before surgery show that high intake of folate has no effect on the plasma concentrations of Hcy. However, Hcy in the group of rats that received 10-fold supplement of folic acid was significantly higher than the control group at the end of the behavioral tests. Our results indicate that high intake of folic acid provides anti-Parkinsonism effect in a dose dependent manner, but this effect is not mediated by lowering plasma Hcy.