Neural control of intestinal ion transport and paracellular permeability is altered by nutritional status.

This study examined the effect of fasting on the neural control of ion transport and paracellular permeability in piglet jejunum. Muscle-stripped tissues from fed or 48-h fasted piglets were mounted in Ussing chambers. Neural blockade with tetrodotoxin (TTX) or antagonists of muscarinic or nicotinic receptors caused reductions in basal short-circuit current that were approximately threefold greater in fasted piglets. The TTX-induced reduction in short-circuit current in fasted piglets was due to a decrease in residual ion flux and was abolished in the absence of HCO(-)(3). Intestinal paracellular permeability, as indicated by tissue conductance (G(t)) and fluxes of inulin and mannitol, was significantly increased by fasting. TTX increased inulin flux and G(t) in fed but not fasted piglets. In fasted piglets, carbachol reduced G(t) by 29% and mannitol flux by 27% but had no effect on these parameters in the fed state. We conclude that fasting enhances enteric neural control of basal ion transport and increases paracellular permeability in piglet jejunum. Tonic release of enteric neurotransmitters regulates paracellular permeability in the fed state, and cholinergic stimulation restores fasting-induced elevations in paracellular permeability to fed levels.