PACAP (1-38) free acid, an endogenous neuropeptide, potently modulates gastrointestinal and neuroendocrine functions. It enhances antral motility, increases somatostatin secretion, and stimulates the release of vasoactive intestinal polypeptide, gastrin releasing peptide, and substance P, while concurrently inhibiting gastrin secretion. Additionally, it augments N-methyl-D-aspartate receptor function and upregulates brain-derived neurotrophic factor expression via RACK1 [1] [2].