VIP (Vasoactive Intestinal Peptide) is a 28–amino acid neuropeptide that was first isolated from the small intestine of pigs. It serves as an important signaling molecule in both the central and peripheral nervous systems and has been extensively researched for its wide-ranging roles in vasodilation, immune regulation, and cellular communication. As part of the glucagon/secretin peptide family, VIP has attracted significant interest in fields such as neuroscience, immunology, and pulmonary research.

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VIP exerts its effects by binding to specific G protein–coupled receptors (VPAC1 and VPAC2) located in tissues like the lungs, gastrointestinal tract, and central nervous system. This binding triggers intracellular signaling pathways that elevate cyclic AMP (cAMP) levels, resulting in smooth muscle relaxation and improved blood flow. In addition, VIP influences immune cell function, helping to reduce inflammation and support tissue repair. Its neuroprotective properties are associated with enhanced neuron survival and decreased oxidative stress. Altogether, these actions position VIP as a key regulator of vascular function, digestion, and immune system balance.