On the contrary, the TH immunohistochemistry results shown that number of DA neurons in the L-DOPA group was not significantly higher than that in the MPTP group, which further illustrates the current major drawbacks of L-DOPA treatment with PD, these drugs can only improve symptoms, but cann’t effectively delay the progression of the disease and prevent the apoptosis of dopamine neurons. The gene discussed is TH; the disease is Parkinson disease.