PACAP STIMULATES PANCREATIC EXOCRINE SECRETION VIA THE VAGAL CHOLINERGIC NERVES IN SHEEP

The present study evaluates the possible role of the vagus nerves in m ediating the stimulatory effect of PACAP-27, PACAP-38 and VIP on the e xocrine pancreas, especially on enzyme secretion which is atropine sen sitive in sheep. The animals were equipped with two cannulae into the common bile duct, a duodenal cannula, and a ruminal cannula under anes thesia. The bilateral cervical vagus nerves were coiled with a cooling device. In conscious animals, the peptides were infused intravenously for 10 min at 10 pmol kg(-1) min(-1) in phase II of the duodenal migr ating motor complexes and the same peptide infusion was repeated in th e reversible cooling blockade of the vagus nerves. Increment in fluid secretion was not significantly altered by the vagal blockade in all t he peptide infusions, while increment in bicarbonate ion by only PACAP -27 was inhibited by the vagal blockade. Increments in protein and amy lase output decreased significantly to 32.0+/-5.0 and 23.2+/-2.6% in P ACAP27, and to 26.1+/-7.7 and 20.8+/-6.4% in PACAP-38 in the vagal blo ckade, but the increments by VIP did not decrease. These results demon strate that circulating PACAP stimulates pancreatic enzyme secretion v ia the vagal cholinergic preganglionic neurons in sheep, suggesting th e central action of PACAP. (C) 1997 Elsevier Science B.V.