TH and Parkinson disease: However, the effect was significantly more pronounced in L2-PD neurons as compared with CTL, as shown by higher percentage of TH+ neurons (Figure 3, B and C; CTL neurons, P < 0.05; L2-PD neurons, P < 0.01) and increased neurite complexity (Figure 3, D–F; CTL neurons, P < 0.05; L2-PD neurons, P < 0.001).