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Vasoactive intestinal peptide (VIP) is a peptide hormone containing 28 amino acid residues and is produced in the pancreas. Its role in the intestine is to greatly stimulate secretion of water and electrolytes, as well as dilating intestinal smooth muscle, dilating peripheral blood vessels, stimulating pancreatic bicarbonate secretion, and inhibiting gastrin-stimulated gastric acid secretion. It is also found in the brain and some autonomic nerves. One region of the brain includes a specific region of the suprachiasmatic nuclei (SCN), which is the location of the 'master circadian pacemaker'. Given that the SCN is responsible for detecting ambient light communicated directly from the retina, and communicating this 'time of day' information to the rest of the body, it is likely that VIP plays a key role in the mammalian time keeping machinery. VIP is also found in the heart and has significant effects on the cardiovascular system. It causes coronary vasodilation as well as having a positive inotropic and chronotropic effect. Research is being performed to see if it may have a beneficial role in the treatment of heart failure. It has a half-life in the blood of about 2 minutes. VIP is overproduced in VIPoma.
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