TH and Parkinson disease: It is well known that GDNF acts as a prominent neurotrophic factor in the DA system and prevents neuronal apoptosis induced by 6-OHDA.39 Moreover, GDNF promotes the survival of dopaminergic neurons after exposure to MPTP.40 Studies have demonstrated that GDNF treatment increased DA release in the striatum.41,42 High expression of GDNF markedly increases TH-positive neurons in the SNpc, which leads to a reduction in dyskinesia in the MPTP-induced PD.30 In this research, we found that PB treatment could increase the expression of GDNF, as revealed by immunohistochemistry.