For example, Yu et al. (2020) found that cell-penetrating peptide (TAT) labeling of vasoactive intestinal peptide (VIP) could positively allosterically modulate the neuropeptide receptor PACAP type 1 receptor (PAC1) and enhance VIP neuroprotection in a mouse model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in PD, which may be useful for developing therapeutic agents for ND. This evidence concerns the gene VIP and Norrie disease.