Dopaminergic Agonists and Muscarinic Antagonists Improve Lateralization in Hemiparkinsonian Rats in a Novel Exploratory Y-Maze

Parkinson’s disease (PD) is characterized by the degeneration of nigrostriatal dopaminergic neurons. Its primary clinical symp-toms are akinesia, tremor, and rigidity, which usually start from one side, resembling the lateralization in hemiparkinsonian rats having 6-hydroxydopamine-induced unilateral lesion of the me-dial forebrain bundle. A novel exploratory Y-maze was de-signed to detect the lateralization of hemiparkinsonian rats in terms of biased turns in the maze. Dopamine agonists levodopa (L-3,4-dihydroxyphenylalanine, 10–30 mg/kg) and apomor-phine (0.1–0.3 mg/kg), but not methamphetamine (0.5–2 mg/ kg), improved the lateralization in the rat model. However, high doses of the dopamine agonists, 30 and 0.3 mg/kg, respec-tively, caused small movements in the arms that seemed to parallel the increase in counts per turn in the Y-maze. Interest