Classical Model of 6-Hydroxydopamine-Induced Parkinsonism in Rats Is Characterized by Unilateral Lesion of Brain Mesolimbic System

—Localizing lesions in the brain of rodents after administration of neurotoxic 6-hydroxidopamine (6-OHDA) is important for understanding the mechanisms of progression of parkinsonism. The present study provides the results of behavioral tests, immunohistochemistry, and measurements of dopamine (DA) level in different areas of the striatum 25 days after unilateral intranigral injection of 6-OHDA to rats. Neuronal death was observed in the both pars compacta of the substantia nigra and the lateral nucleus of the ventral tegmental area (VTA). Detailed analysis of DA levels showed a 90% decrease in the dorsal striatum and a 73% decrease in the ventral striatum only at the side ipsilateral to toxin injection. The changes discovered in VTA are similar to the results of morphological post mortem studies of Parkinson’s disease. Previously described emotional disturbances in rats with 6-OHDA-induced Parkinson’s disease may be related to the damage in VTA shown in our study.