Release of vasoactive intestinal peptide by intraduodenal infusion of HCl or fat and intramuscular injection of neostigmine in man.

A highly sensitive radioimmunoassay system for plasma vasoactive intestinal peptide (VIP) was developed to examine the effect of intraduodenal infusion of HCl or fat on the plasma VIP levels in healthy subjects, and the effect of intramuscular injection of neostigmine in patients with irritable bowel syndrome (IBS). Intraduodenal infusion of 100 ml of 0.1 N HCl or 10 g fat caused a significant rise in plasma VIP level. Neostigmine (12.5 micrograms/kg) produced a significant rise in plasma VIP level, and the plasma VIP response to neostigmine was significantly greater in the IBS group than in the normal group. These results suggest that VIP might play a role in the pathophysiology of IBS.