Abstract: Levodopa is the gold-standard treatment for Parkinson’s disease. However, although it alleviates the clinical symptoms, it cannot delay the progressive apoptosis of dopaminergic neurons or prevent motor complications in the long term. In the present study, we investigated the e?ect of Shudipingchan granule on neuronal apoptosis in a rat model of Parkinson’s disease, established by injecting 6-hydroxydopamine into the substantia nigra pars compacta and ventral tegmental area. We then administered levodopa (20 mg/kg intraperitoneally, twice daily) with or without Shudipingchan granule (7.5 mL/kg intragastrically, twice daily), for 4 weeks. Te long-term use of levodopa accelerated apoptosis of nigral cells and worsened behavioral symptoms by activating the extracellular signal-regulated kinase pathway and downstream apoptotic factors. However, administration of Shudipingchan granule with levodopa reduced expression of phosphorylated extracellular signal-regulated kinase 1/2 and Bax, increased tyrosine hydroxylase and Bcl-2, reduced apoptosis in the substantia nigra, and markedly improved dyskinesia. Tese fndings suggest that Shudipingchan granule suppresses neuronal apoptosis by inhibiting the hyperphosphorylation of extracellular signal-regulated kinase and downregulating expression of anti-apoptotic genes. Shudipingchan granule, used in combination with levodopa, can e?ectively reduce the symptoms of Parkinson’s disease.

Key words: nerve regeneration, Parkinson’s disease, levodopa, substantia nigra, apoptosis, Shudipingchan granule, extracellular signal-regulated kinase pathway, behavior, neural regeneration