Intestinal epithelium sensitivity to acetylcholine varies with age and intestinal location in piglets

Objectives and Study: Defaults in intestinal barrier function, including altered tight junction permeability and electrolyte secretion, are involved in various diseases in children but little is known about its nervous regulation and its postnatal maturation. The aim of our study was to describe the evolution of intestinal barrier permeability and electrolyte secretion within the first month of life and its regulation by the cholinergic system in piglets. Methods: 28 suckling piglets were sacrificed at age 0, 2, 14 and 28 days. Jejunum, ileum and colon were sampled to study intestinal barrier function in Ussing chamber. Short-circuit current (Isc) and flux of FITC-dextran 4000 (FD4) were used to evaluate electrolyte secretion and paracellular permeability, respectively. Cholinergic modulation was investigated by the use of carbachol, a cholinergic agonist. Acetylcholine esterase (AChE) assay was performed on each level of the bowel at each age to describe acetylcholine catabolism. Results: An age effect was identified for most of the parameters studied, yet with different patterns depending on the location and the parameter considered. In the jejunum, FD4 flux increased with age (+420%, P<0.05) while Isc decreased sharply after birth (-64%, P<0.05). Cholinergic stimulation tended to reduce FD4 flux (-50%, P=0.11) at birth with no further effect on jejunal permeability in older piglets. In contrast, carbachol-induced electrolyte secretion increased with age (+317%, P<0.05). A similar pattern was observed in the ileum, although basal Isc decrease with age occurred later, between d14 and d28 (-830%, P<0.05). Conversely, in the colon although basal FD4 flux and Isc post-natal evolution trend was similar than in the small intestine, the changes were more progressive and with less amplitude within the first month of life (difference between d0 and d28: FD4 flux +162%, P<0.05 and Isc -70%, P=0.08). Opposite to the small intestine, carbachol had no effect on colonic FD4 flux at any age and induced electrolyte secretion at birth but not in older piglets. AChE activity decreased sharply (-50%, P<0.05) between birth and day 2 in the jejunum with no further changes with age and was stable with time in the ileum. In the colon, AChE activity was nearly 10 times higher and decreased progressively with age (-22% between d0 and d28, P<0.05). Conclusion: Our study demonstrates that intestinal epithelial cell sensitivity to acetylcholine differs with post-natal age in piglet small and large intestine. It also emphasizes the need for more studies to understand how, where and when cholinergic system modulates the intestinal barrier.