Sympathetic control of motility, fluid transport, and transmural potential difference in the rabbit ileum

Both intestinal motility and intestinal fluid and electrolyte transport are influenced by the sympathetic nervous system. The aim of this study is to examine the relationship between the sympathetically induced inhibition of spontaneous contractile activity and epithelial function, monitoring simultaneously motility, fluid transport, and transmural potential difference (PD) in the rabbit ileum. Experiments were performed in vitro to eliminate any possible indirect effects on intestinal function caused by alterations in intestinal blood flow. Perivascular nerve stimulation induced an inhibition of spontaneous motility, a fall in transmural PD (toward more lumen positive), and an enhanced fluid absorption. The sympathetically induced inhibition of motility was abolished by the beta-adrenoceptor antagonist, propranolol, whereas the subsequent administration of phentolamine, the alpha-adrenoceptor antagonist, was required to abolish the fall in transmural PD. Thus the sympathetic nervous system is capable of simultaneously influencing intestinal motility and fluid and electrolyte function. However, separate but parallel neural mechanisms control the smooth muscle and epithelial responses; the inhibition of motility is beta-mediated, while alpha-receptors alter fluid and electrolyte transport.