Evidence for vip-induced increase in no production in the myenteric
neurons of opossum internal anal sphincter.
Chakder, Sushanta, Satish Rattan.
Department of Medicine, Division of Gastroenterology and
Hepatology, Thomas Jefferson University, Philadelphia, PA 19107
APStracts 2:0211G, 1995.
A significant interaction between vasoactive intestinal polypeptide
(VIP) and nitric oxide (NO) has been reported in the
neurotransmission of the gastrointestinal tract including the
internal anal sphincter (IAS). The exact site of this NO release from
the IAS in response to VIP is not known. The studies were carried out
to determine the site of VIP-induced NO release in the opossum IAS.
The NO synthase (NOS) activity was quantitated by determining L
-[3H]citrulline production from L-[3H]arginine in the isolated
myenteric ganglia and the smooth muscle cells of the IAS. L
-[3H]citrulline production was determined before and after treatment
with either the ganglionic stimulant DMPP, VIP or peptide histidine
isoleucine (PHI) in the absence and presence of the neurotoxin
tetrodotoxin and the NOS inhibitor L-NNA. The smooth muscle cells and
the ganglia were preloaded with L-[3H]arginine for 5 min and treated
with VIP for 1 and 5 min. DMPP and VIP caused significant increase in
the L-[3H]citrulline production in the myenteric ganglia while PHI
had no effect. VIP caused a significant increase in the L
-[3H]citrulline formation in myenteric ganglia at both time periods,
while in the smooth muscle cells there was a moderate but significant
increase in L-[3H]citrulline formation only at 5 min of VIP
treatment. VIP-induced relaxation of isolated smooth muscle cells of
the IAS was not affected by L-NNA. The increase in the NOS activity
of myenteric ganglia by DMPP and VIP was sensitive to the neurotoxin
and the NOS inhibitor. The data suggest that the increase in NO
production in response to VIP in the IAS occurs mainly from the
myenteric neurons with some contribution from the smooth muscle
cells.
Received 14 December 1994; accepted in final form 20 September
1995.
APS Manuscript Number G489-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95