TACHYKININS INFLUENCE INTERDIGESTIVE RHYTHM AND CONTRACTILE STRENGTH OF HUMAN SMALL-INTESTINE

The effect of the putative enteric neurotransmitters neurokinin A and substance P were investigated on human small intestinal motility, Eith er neurokinin A, at doses of 6-25 pmol/kg/min, or substance P at doses of 1-6 pmol/kg/min were administered intravenously to healthy volunte ers over 4 hr, Neurokinin A dose-dependently increased the fraction of phase II of the migrating motor complex, contraction frequency, motil ity index, and amplitude of contractions, At the highest dose, neuroki nin A induced a phase II-like pattern, disrupting the migrating myoele ctric complex. Substance P dose-dependently increased phase II of the migrating motor complex. The contraction frequency increased slightly at the highest dose, but neither motility index nor contraction amplit ude changed. It is concluded that neurokinin A and substance P stimula te small intestinal motility in man, and it can be speculated that the y play a role in the control of human small intestinal motility.