VIP is localized in nerve fibers of the central and peripheral nervous system, and is probably acting as a neurotransmitter. Smooth muscle relaxation, vasodilation and secretion from exocrine glands are some of the effects of VIP. The Verner-Morrison or Watery Diarrhea Hypokaliemia and Achlorhydria (WDHA) syndrome is a characteristic clinical syndrome associated with overproduction of VIP from endocrine tumors. These VIP-producing tumors are usually neuroblastomas of endocrine tumors in the pancreas. Absorption with 10-100 µg immunogen per ml diluted antiserum abolishes the staining, while PHI, secretin, glucagon, GIP, and CCK do not.
Positive control: Formalin-fixed paraffin sections of cat ileum.