Contrasting cholinergic dependence of pancreatic and gallbladder responses to cholecystokinin.

ABSTRACT

Cholinergic receptors for cholecystokinin (CCK) have been identified on neurons of the enteric nervous system, including those of the gallbladder. To determine whether any differences exist in the extent to which CCK action depends on muscarinic cholinergic receptors in the pancreas and gallbladder, 11 dogs with pancreatic and 7 dogs with biliary fistulas were given increasing doses of intravenous CCK-8 (15-250 ng X kg-1 X h-1) or intraduodenal sodium oleate (0.1-9 mmol/h) with and without atropine pretreatment. Pancreatic protein response to CCK-8 was dose dependent, reaching a maximal of 448 +/- 76 mg/15 min at the highest dose. Atropine pretreatment caused nonsignificant reduction in the response to the lowest dose but had no effect on the responses to the other doses, with the response to the highest dose of CCK being 473 +/- 82 mg/15 min. In contrast, gallbladder contraction as measured by bile fistula bilirubin output was very sensitive to inhibition by atropine. Bilirubin responses to 16, 32, 62.5, 125, and 250 ng X kg-1 X h-1 were 14 +/- 5, 18 +/- 5, 28 +/- 5, 36 +/- 6, and 52 +/- 12 mg/h, respectively, without atropine and 0 +/- 0, 6 +/- 2, 7 +/- 2, 18 +/- 4, and 18 +/- 4 mg/h with atropine pretreatment. Similarly, pancreatic responses to sodium oleate infusion were less susceptible to inhibition by atropine than were the gallbladder responses. With respect to pancreatic protein secretion, the response to only the lowest dose of sodium oleate was significantly inhibited by atropine.(ABSTRACT TRUNCATED AT 250 WORDS)