The postnatal maturation of exocrine pancreatic function has been demonstrated in human neonates (Zoppi et al. 1972), rats (Chang & Jamieson, 1986), calves (Track et al. 1972; Le Huërou-Luron et al. 1992), lambs (Guilloteau et al. 1983) and pigs (Corring et al. 1978; Weström et al. 1987; Baintner & Farkas, 1989; De Passille et al. 1989). In pigs, it has been confirmed that the maturation of exocrine pancreatic function is age dependent (Corring et al. 1978; Lindemann et al. 1986). However, it has also been reported that the weaning-induced maturation of exocrine pancreatic secretion is not dependent upon age (Pierzynowski et al. 1991, 1993, 1995; Rantzer et al. 1997). In calves, the well-established age/weaning-related changes in the secretion pattern of gastrointestinal tract hormones are in agreement with this hypothesis (Le Huërou-Luron & Guilloteau, 1999; Zabielski et al. 1999). It has been shown that in pigs, the response of the exocrine pancreas to exogenous secretagogues is also dependent upon age (Harada et al. 1988) and weaning status (Pierzynowski et al. 1988, 1990, 1999). However, there is limited data available concerning the role of the neural regulatory pathways in the maturation of exocrine pancreas function in pigs. It has been demonstrated that in growing pigs, extrinsic innervation from the parasympathetic nervous system plays a significant regulatory role in exocrine pancreatic secretion (Holst et al. 1979; Pierzynowski et al. 1994). In addition, it has been reported that in neonatal The role of cholinergic and peptidergic pathways in the regulation of pancreatic exocrine function during postnatal development in pigs V. Lesniewska*†‡, A. Gregard†, B. Weström†, M. S. Hedemann§, H. N. Lærke §, D. Kruszewska† and S. G. Pierzynowski†¶ *Department of Animal Physiology, Faculty of Veterinary Medicine, Warsaw Agricultural University, ul. Nowoursynowska 166, 02-787 Warsaw, Poland, †Department of Animal Physiology, Lund University, Helgonavagen 3b, S-223 62 Lund, Sweden, §Department of Animal Nutrition and Physiology, Danish Institute of Agricultural Sciences, Research Centre Foulum, PO Box 50, DK-8830 Tjele, Denmark and ¶ R. & D. Gramineer Int. AB, Ideon, 223 70 Lund, Sweden (Manuscript received 18 October 2000; accepted 6 February 2001) The aim of this study was to investigate the role of the parasympathetic (cholinergic and peptidergic) nervous system in the regulation of exocrine pancreas function in piglets during their early postnatal development. The cholinergic and peptidergic regulatory pathways of exocrine pancreatic function were tested by the specific muscarinic receptor blocker 4-diphenylacetoxy-N-methylpiperidine-methiodide (4-DAMP) and bombesin, respectively. At the age of 2 weeks, piglets were surgically fitted with a chronic pancreatic duct 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, the output of total protein and the activity of trypsin, chymotrypsin, carboxyl ester hydrolase and amylase during preprandial and postprandial pancreatic secretion, in both the pre- and post-weaning periods. However, the inhibitory effect of 4-DAMP during postprandial secretion was significantly greater (P< 0.05) in suckling piglets. The infusion of bombesin (10, 100 and 1000 pmol kg _1 h _1 ) stimulated exocrine pancreatic secretion in a dose-dependent manner during both the pre- and post-weaning periods. However, the stimulatory effect of 1000 pmol kg _1 h _1 bombesin on total protein output and the activities of trypsin, chymotrypsin and amylase were significantly higher (P< 0.05) in suckling piglets. In summary, our study showed that cholinergic and peptidergic mechanisms are involved in the regulation of exocrine pancreas function in piglets in both the pre- and post-weaning stages. 4-DAMP had a greater inhibitory effect on exocrine pancreatic secretion in piglets during the pre-weaning period. Thus, these observations suggest that the parasympathetic nervous system plays a dominant role in the functioning of the exocrine pancreas at this time. The action of bombesin suggests that it is a potent secretagogue for the exocrine pancreas in pigs during their postnatal development. Experimental Physiology (2001) 86.3, 399–409. 2151 Publication of The Physiological Society ‡ Corresponding author: lesniewska@alpha.sggw.waw.pl ) by guest on July 14, 2011 ep.physoc.org Downloaded from Exp Physiol (