Isatin, an endogenous MAO inhibitor, improves bradykinesia and dopamine levels in a rat model of Parkinson's disease induced by Japanese encephalitis virus

Isatin, an endogenous monoamine oxidase (MAO) inhibitor, has an important role in the control of neurotransmitter concentration. We previously reported that exogenously administered isatin significantly increased acetylcholine (ACh) and dopamine (DA) levels in the rat striatum. In order to test the possibility of treating Parkinson's disease by isatin, we evaluated DA levels in the striatum and bradykinesia using a rat model of Parkinson's disease induced by the Japanese encephalitis virus (JEV). We have already reported that in adult Fischer rats infected with JEV at day 13, there was a marked decrease of tyrosine hydroxylase-positive neurons in the bilateral substantia nigra after 12 weeks. Effects of isatin were investigated in JEV-induced post-encephalitic parkinsonism rats by a pole test and high performance liquid chromatograph (HPLC) with an electrochemical detector (ECD). Isatin (100 mg/kg per day for 1 week, intraperitoneal injection) improved the bradykinesia observed in the JEV-induced parkinsonism rats. Dopamine (DA) concentrations in the JEV-infected rats were profoundly reduced in the striatum as compared with controls. Isatin also increased DA in the striatum of parkinsonism rats. These results suggest that isatin could be a possible treatment for Parkinson's disease as well as for post-encephalitic parkinsonism.