AJP - Gastrointestinal and Liver Physiology, Vol 259, Issue 2 252-G257, Copyright © 1990 by American Physiological Society
VIP antagonist [N-Ac-Tyr1,D-Phe2]-GRF-(1-29)-NH2: an inhibitor of vasodilation in the feline colon
M. A. Blank, K. Kimura, M. Fuortes and B. M. Jaffe
Department of Surgery, State University of New York Health Science Center, Brooklyn 11203.
The effect of the vasoactive intestinal polypeptide (VIP) antagonist
[N-Ac-Tyr1,D-Phe2]-GRF-(1-29)-NH2 on pelvic nerve-induced colonic
vasodilation and VIP release was investigated in chloralose-anesthetized
cats. VIP antagonist (10 and 50 nmol/kg in saline) or saline alone was
injected into a branch of the superior mesenteric artery immediately before
bilateral pelvic nerve stimulation. The increase in conductance in the
inferior mesenteric artery during pelvic nerve stimulation was reduced in
an apparently dose-dependent fashion by the VIP antagonist (by 35 +/- 10
and 42 +/- 9%, respectively) compared with the pelvic nerve-induced
increase in conductance after injection of saline alone. Injection of the
VIP antagonist (50 nmol/kg) did not alter conductance in the absence of
pelvic nerve stimulation. VIP was released into portal venous blood during
pelvic nerve stimulation in the presence of the antagonist (from 103 +/- 29
to 165 +/- 45 pmol/l). This was not significantly different from release in
the presence of saline. The effect of the VIP antagonist (10
nmol.kg-1.min-1) on inferior mesenteric arterial vasodilation induced by
exogenous VIP was also quantitated. The increase in conductance after VIP
injection (0.2 nmol/kg) was significantly reduced when accompanied by
simultaneous infusion of the VIP antagonist (by 54 +/- 6%) compared with
the increase in conductance during simultaneous infusion of saline. We
conclude that [N-Ac-Tyr1,D-Phe2]-GRF-(1-29)-NH2 is an inhibitor of pelvic
nerve-induced vasodilation in the feline colon and does not act by
modulating VIP release.(ABSTRACT TRUNCATED AT 250 WORDS)
