AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 6 847-G851, Copyright © 1986 by American Physiological Society
Dose-response effects of atropine on pancreatic secretory response to intestinal tryptophan in dogs
J. Vazquez-Echarri, D. Baumgartner and M. V. Singer
In dogs with gastric and pancreatic fistulas, we studied the effect of
intravenous infusion of atropine in doses of 0.9, 1.8, 7, and 29 nmol X
kg-1 X h-1 on the pancreatic secretory response to graded loads of
intraduodenal infusions of tryptophan, given with a secretin background.
Infusions of 1.8, 7, and 29, but not 0.9 nmol X kg-1 X h-1 of atropine
sulfate significantly (P less than 0.05) decreased the incremental protein
response to all loads of tryptophan. The cumulative incremental protein
output was reduced by 44, 37, and 52%, respectively. Infusions of 1.8, 7,
and 29 nmol X kg-1 X h-1 of atropine significantly decreased by
approximately 50% the incremental bicarbonate response to low (0.12 and
0.37 mmol/h) but not high loads (1.1, 3.3, and 10 mmol/h) of tryptophan.
The inhibitory potency of the effective doses of atropine did not differ
significantly. Only the highest dose of atropine significantly increased
heart rate by 76%. These findings indicate that 1) in the intact animal,
the minimal dose of atropine required for inhibition of pancreatic
bicarbonate and protein response to intraduodenal tryptophan seems to be
1.8 nmol X kg-1 X h-1, a dose that causes probably few systemic effects,
since it does not increase heart rate; and 2) the inhibitory action of
atropine on the pancreatic response to tryptophan appears to be an
"all-or-none" effect.
