After treatment with Guiling pa'an Wan, the expression of Bcl-2 and Bcl-2/Bax ratio was increased while Bax and Caspase-3 expression were dropped in substantia nigra neurons, which showed that Guiling pa'an could provide protection for dopaminergic neurons by reducing the apoptosis of nerve cells in PD rats (Meng et al., 2014b; Zhang H. Z. et al., 2016). This evidence concerns the gene BAX and Parkinson disease.