ADCYAP1 encodes pituitary adenylate cyclase-activating peptide (PACAP), a neuropeptide that exists in two bioactive forms, PACAP27 and PACAP38, generated from proteolytic processing 1. PACAP activates G protein-coupled receptors including VIPR1, VIPR2, and ADCYAP1R1 to mediate diverse physiological functions 23. The peptide exerts neuroprotective and cytoprotective effects through anti-apoptotic, anti-inflammatory, and antioxidant mechanisms, while promoting neuron projection development via the RAPGEF2/Rap1/B-Raf/ERK pathway 3. PACAP enhances axon outgrowth in sensory neurons and is significantly upregulated during peripheral nerve regeneration; its expression correlates with intraepidermal nerve fiber recovery following carpal tunnel decompression 4. The neuropeptide also regulates glucose homeostasis and insulin secretion in pancreatic beta cells. Clinically, PACAP signaling is implicated in migraine pathophysiology, with PACAP activating mast cell MRGPRX2 receptors to drive migraine-like pain 5. Additionally, altered ADCYAP1 expression and the downstream cAMP/PKA/NMDAR pathway are associated with schizophrenia pathophysiology, particularly social withdrawal symptoms; PACAP restoration can reverse social behavioral deficits in preclinical models 67. PACAP/PAC1 signaling also modulates lower urinary tract function and may represent a therapeutic target for bladder pain syndrome 8.