Levodopa (L-dopa) is the key component in Parkinson's disease (PD) treatment. Recently, we demonstrated that beta-asarone improves the motor behavior of rats with unilateral striatal 6-hydroxydopamine lesion. Striatal level of dopamine (DA) and L-dopa increased after beta-asarone and L-dopa co-administered treatment in healthy rat. Since its effects and mechanisms on PD rats are still unclear, we investigated whether coadministration could help treat PD rats. Here, PD rats were randomly divided into seven groups (n = 10/group): an untreated group, a Madopar-treated group, a L-dopa-treated group, a beta-asarone-treated group, and groups receiving low, medium or high doses of beta-asarone respectively plus the same dose of L-dopa. The sham-operated group rats were injected with saline. Treatments were administered to the rats twice per day continuously for 30 days. The behavioral tests were assessed. Neurotransmitters, dopa decarboxylase (DDC), tyrosine hydroxylase (TH), catechol-O-methyltransferase (COMT), monoamine oxidase B (MAO-B) and dopamine transporter (DAT) levels were detected. The pathological characteristics of liver and kidney and ultrastructure of dopaminergic neurons were observed. The behavior of PD rats improved significantly after co-administered treatment compared with the untreated group. In addition, our results also showed that co-administered treatment increased L-dopa, DA, DOPAC, HVA and 5-HT levels, enhanced the MAO-B, COMT, TH and DAT levels, reduced creatinine level, decreased the amount of lysosome and mitochondria and showed no liver and kidney toxicity. These findings suggest that co-administered treatment could elevate striatal levels of L-dopa and DA and improve the behavioral abilities in PD rats by regulating the DDC, TH, MAO-B, COMT and DAT levels. (C) 2017 Elsevier Masson SAS. All rights reserved.