The role of cholinergic and peptidergic pathways in the regulation of pancreatic exocrine function during postnatal development in pigs

The aim of this study was to investigate the role of the parasympathetic (c holinergic and peptidergic) nervous system in the regulation of exocrine pa ncreas function in piglets during their early postnatal development. The ch olinergic and peptidergic regulatory pathways of exocrine pancreatic functi on were tested by the specific muscarinic receptor blocker 4-diphenylacetox y-N-methylpiperidine-metiodide (4-DAMP) and bombesin, respectively. At the age of 2 weeks, piglets were surgically fitted with a chronic pancreatic du ct catheter, a duodenal re-entrant cannula and a jugular vein catheter, The experiments comprised a pre-weaning period, and a post-weaning period that commenced at the beginning of the 5th week of age. Intravenous infusion of 4-DAMP (100 pmol kg(-1) h(-1)) reduced the outflow of pancreatic juice, th e output of total protein and the activity of trypsin, chymotrypsin, carbox yl ester hydrolase and amylase during preprandial and postprandial pancreat ic secretion, in both the pre- and post-meaning periods. However, the inhib itory effect of 4-DAMP during postprandial secretion was significantly grea ter (P < 0.05) in suckling piglets, The infusion of bombesin (10, 100 and 1 000 pmol kg(-1) h(-1)) stimulated exocrine pancreatic secretion in a dose-d ependent manner during both the pre- and post-weaning periods. However, the stimulatory effect of 1000 pmol kg(-1) h(-1) bombesin on total protein out put and the activities of trypsin, chymotrypsin and amylase were significan tly higher (P < 0.05) in suckling piglets. In summary, our study showed tha t cholinergic and peptidergic mechanisms are involved in the regulation of exocrine pancreas function in piglets in both the pre- and post-weaning sta ges, 4-DAMP had a greater inhibitory effect on exocrine pancreatic secretio n in piglets during the pre-weaning period. Thus, these observations sugges t that the parasympathetic nervous system plays a dominant role in the func tioning of the exocrine pancreas at this time. The action of bombesin sugge sts that it is a potent secretagogue for the exocrine pancreas in pigs duri ng their postnatal development.