The neuroprotective effects of a standardized extract of Ginkgo biloba L. (EGb 761) were investigated on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in the nigrostriatal dopaminergic system of the rat brain. Rats were given a week of pretreatment with daily administrations of EGb 761. Unilateral striatal injection of 6-OHDA was followed by treatment with EGb 761 for a week. Serial measurement of contralateral forepaw adjusting steps revealed a progressive deficit in motor activity. At 8 weeks after 6-OHDA lesion the number of contralateral forepaw adjusting steps was significantly higher in rats that were treated with high doses of EGb 761 (100 mg/kg daily) than in those treated with low doses (50 mg/kg) or with the vehicle. Dopamine neuron loss in the substantia nigra and a depletion in striatal dopamine corresponded with behavioural deficit. These data suggest that the neuroprotective effects of EGb 761 reduce the behavioural deficit in 6-OHDA lesions in rat and also indicates a possible role for the extract in the treatment of Parkinson's disease.

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