Evaluation of Apoptosis and Neuronal Changes in the Compact Part of Substantia Nigra and Striatum Following the Use of Levodopa and Levodopa -Benserazide in Parkinson’s Rats

Background: Parkinson’s disease is a common and progressive neuropathology disorder caused by the neuronal degradation of the dopaminergic system of the substantia nigra. We investigated the increase of levodopa in the brain to protect neurons. Methods: Twenty eight male Wistar rats (weighing 200 - 250 grams) were randomly divided into four groups (n = 7 each). The control group received only saline. The second group used MPTP toxin to create Parkinson’s disease. The third group received levodopa 10 mg/kg intraperitoneally and the fourth group received levodopa 10 mg/kg plus benserazide 2.5 mg/kg intraperitoneally for two weeks. All rats were decapitated after four weeks and their brains were prepared for the TUNNEL and immunohistochemical studies. Results: Immunohistochemistry results showed that the number of tyrosine hydroxylase (TH) positive neurons in the substantia nigra (SNpc) region was significantly higher in the combined treatment group than in the other groups, and the number of TUNNEL positive cells in this group was lower than in the other treatment groups. Conclusions: The results show there is a positive correlation between behavioral improvements and TH positive cells. Therefore, it is possible that the increase of levodopa in the brain leads to behavioral improvement. Increasing amount of levodopa in the brain reduces the number of apoptotic cells. Therefore, there is a direct correlation between the level of brain levodopa and cell death. Thus, we suggest that the increase in dopamine in the brain following the use of benserazide can support the dopaminergic neurons of the SNpc.