and Objective: Parkinson's disease (PD) is a neurodegenerative disease with selective damage of mesencephalic dopaminergic neurons. Due to the protective, anti-inflammatory, and antioxidant effect of Hypericum perforatum (HP), this study was undertaken to assess dose-dependent effect of HP hydroalcoholic extract on motor imbalance following intrastriatal injection of 6-hydroxydopamine in the rat. Materials and Methods: In this experimental research, male Wistar rats (n=35) were equally divided

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... nto sham, 6-hydroxydopamine (OHDA)-lesioned, and HP extract-treated lesion groups. Model of PD was induced by microinjecting 12.5 microgram of 6-OHDA dissolved in saline-ascorbate solution into the left striatum. Treated lesion groups received HP extract at doses of 50, 100, and 200 mg/kg/day p.o. started one week before the surgery for 1 week post-surgery. After 1 week, ipsilateral and contralateral rotations induced by apomorphine were counted and net scores were obtained. Results: In the 6-OHDA-lesioned group, the dopaminergic agonist apomorphine induced contralateral rotational behavior (P<0.001) as compared to sham. In addition, administration of HP extract at doses of 100 and 200 mg/kg significantly reduced the number of contralateral rotations (P<0.05) versus 6-OHDA group. Conclusion: Oral administration of HP extract at doses of 100 and 200 mg/kg could reduce motor imbalance and attenuate forced biased rotational behavior in 6-OHDA-induced model of PD.