AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 1 51-G55, Copyright © 1986 by American Physiological Society
Vasoactive intestinal polypeptide provokes acetylcholine release from the myenteric plexus
M. Kusunoki, L. H. Tsai, K. Taniyama and C. Tanaka
Effects of vasoactive intestinal polypeptide (VIP) on the release of
acetylcholine (ACh) from longitudinal muscle strips with myenteric plexus
(LM) preparations were examined in the guinea pig small intestine. VIP
(10(-10) to 10(-6) M) induced a concentration-dependent contraction of LM
preparation. The VIP-induced contractions seem to be related to three
components, the scopolamine-sensitive, the scopolamine-insensitive, the
tetrodotoxin-sensitive, and the tetrodotoxin-insensitive contractions. VIP
(10(-10) to 10(-6) M) induced a concentration-dependent increase in the
release of [3H]ACh from LM preparations preloaded with [3H]choline. The
VIP-evoked [3H]ACh release was inhibited by removal of Ca2+ from the
perfusion medium and by treatment with tetrodotoxin but not by scopolamine
and hexamethonium. The spontaneous and VIP-evoked [3H]ACh release was not
affected by phentolamine, propranolol, methysergide, diphenhydramine,
cimetidine, bicuculline, or [D-Pro2, D-Trp7,9]substance P. The result
demonstrates that VIP induces contractions of longitudinal smooth muscle
directly and indirectly by the stimulation of both cholinergic neurons and
noncholinergic excitatory neurons.
