On the other hand, PACAP, as an endogenous neuropeptide, proved its neuroprotective roles in neurodegenerative disorders[32,33,34] and also in retinal pathologies such as retinal ischemia [35], excitotoxic retinal injury [36] or in DR [18,21,37,38,39,40]. The gene discussed is ADCYAP1; the disease is retinal ischemia.