Dose-response effects of atropine on pancreatic secretory response to intravenous cerulein in dogs.

In conscious dogs with gastric and pancreatic fistulas, we studied the effect of i.v. atropine in doses ranging from 1.8 to 29 nmol/kg/h on the pancreatic secretory response to i.v. cerulein in doses ranging from 3.7 to 118 pmol/kg/h. Cerulein was given with an i.v. background infusion of secretin (20.5 pmol/kg/h), started 1 h before the lowest dose of cerulein was given. Secretin alone did not stimulate pancreatic protein output above basal. Doses of 7 and 29 nmol/kg/h of atropine significantly (p less than 0.05) decreased the protein output during secretin. A dose of 29 nmol/kg/h, but not lower doses, of atropine significantly inhibited the bicarbonate response to secretin. A dose of 3.7 pmol/kg/h and all higher doses of cerulein significantly stimulated bicarbonate and protein output above the value observed during secretin alone. None of the three doses of atropine given had any significant effect on the incremental bicarbonate and protein responses to cerulein. Secretin and cerulein did not alter basal heart rate; only the highest dose (29 nmol/kg/h) of atropine significantly increased heart rate. These findings are compatible with the hypothesis that cholinergic nerves do not alter the effect of exogenous cerulein, a CCK analogue, on pancreatic bicarbonate and protein secretion in dogs.