ADCYAP1R1 and Huntington disease: Previous studies have demonstrated that PAC1-R mainly mediates the therapeutic effect of PACAP on Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, traumatic brain injury, and stroke in in vivo and in vitro models, indicating that PAC1-R is a clinically important target for drug development for systemic degenerative diseases [6,7].