The importance of the vagus nerves in duodenal acid neutralization
in anaesthetized pigs.
Glad, Henrik, Per Svendsen, Ole Olsen, and Ove B. Schaffalitzky De
Muckadell.
Dept. of Medical Gastroenterology, Odense University Hospital,
Biomedical Laboratory, Odense University, Odense, and Dept. of
Surgery C, Rigshospitalet, University of Copenhagen, Copenhagen,
Denmark
APStracts 3:0140G, 1996.
During the cephalic phase of gastric acid secretion vagally mediated
synchronous stimulation of bicarbonate provides a protection against
the acid. The purpose of this study was to determine simultaneously
the effect of electrical vagal stimulation (EVS) on pancreatic,
hepatic and duodenal mucosal bicarbonate secretion, and thereby
estimate their relative importance in vagally-induced duodenal acid
neutralization. Splanchnicotomy increased vagally-induced
pancreaticobiliary bicarbonate secretion whereas duodenal mucosal
bicarbonate secretion was unchanged. After splanchnicotomy EVS (10
msec, 15 mA, 12 Hz) significantly increased pancreatic bicarbonate
secretion from 0 to 4.17 mmol/h, hepatic bicarbonate secretion from
0.16 to 0.22 mmol/h and duodenal mucosal bicarbonate secretion from
0.17 to 0.31 mmol/h. Pancreaticobiliary bicarbonate secretion was
atropine resistant whereas vagally-induced duodenal mucosal
bicarbonate secretion was diminished by atropine (2.0 mg/kg). After
splanchnicotomy EVS (10 msec, 15 mA, 12 Hz) had no effect on portal
plasma concentration of secretin whereas vasoactive intestinal
peptide was increased from 14 to 29 pM. EVS at 12 Hz with varying
duration (3 or 10 msec) and amplitude (3-50 mA) had no further effect
on the bicarbonate secretion from the three organs. Finally, biliary
[14C]mannitol clearance is not a reliable marker of canalicular bile
secretion in pigs. These results suggest that in the anaesthetized
pig: (1) vagal stimulation is only of minor importance to hepatic
bicarbonate secretion; (2) vagal stimulation stimulates pancreatic
bicarbonate secretion through both cholinergic muscarinic and non
-cholinergic transmission; and (3) vagal stimulation stimulates
duodenal mucosal bicarbonate secretion mainly through cholinergic
muscarinic transmission. In conclusion, these results suggest that
only pancreatic and duodenal bicarbonate production play a role in
vagally-induced duodenal acid neutralization.
Received 3 October 1995; accepted in final form 8 July 1996.
APS Manuscript Number G426-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996