TAC1 and Parkinson disease: In the present study, to further evaluate whether the anti-apoptotic effects of teaghrelin are mediated through the activation of the ERK1/2 pathway, the PD cell model was incubated with the substance P. As shown in Figure 6, ERK1/2 phosphorylation dramatically decreased, and cytochrome c and cleaved caspase-3 levels significantly increased after MPP+ treatment.