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Vasoactive Intestinal Peptide (VIP)

A. Structure

It is a peptide having 28 amino acids. It is formed from its precursor prepro-VIP. Prepro-VIP has VIP and another peptide resembling VIP called PHM-27.


B. Site

VIP is found in the nerves in the GIT, blood (where its T1/2 is 2 minutes), brain and autonomic nerves. In the brain and autonomic nerves, VIP is often found along with acetylcholine.

C. Actions

  1. markedly increases the intestinal secretion of electrolytes and water
  2. relaxes the intestinal smooth muscle, including the sphincters
  3. inhibits gastric acid secretion
  4. increases action of acetylcholine on salivary glands. VIP and acetylcholine co-exist in the nerves to the salivary glands; they do not exist together in other nerves of the GIT.
  5. dilates peripheral blood vessels
  6. VIP secreting tumours (called as VIPomas) cause severe diarrhea

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