ADCYAP1 and Alzheimer disease: Previous studies have shown that PACAP and its receptors are widely distributed in brain tissues, and that PACAP plays a neuroprotective role in neurodegenerative diseases such as stroke (Matsumoto et al., 2016), traumatic brain injury (Toth et al., 2020), Alzheimer’s disease (Han et al., 2014), and Parkinson’s disease (Wang et al., 2008).