Submucosal plexus alone integrates motor activity and epithelial transport in rat jejunum.

It has been well established in several mammalian species, including humans, that contractions of jejunal smooth muscle correlate temporally with increases in mucosal ion transport. Furthermore, this correlation is abolished through local application of neurotoxins, suggesting interaction of enteric neurons. The purpose of this study was to determine whether the myenteric plexus is involved in this correlation. In the rat jejunum in vivo, we simultaneously measured phasic changes in intraluminal pressure and transmural potential difference (PD) as indicators of smooth muscle motor activity and epithelial ion transport, respectively. We compared the temporal association of these parameters in control animals with animals in which either the extrinsic nerves only or the extrinsic nerves and the myenteric plexus of a 5-cm jejunal segment had been ablated 30 days previously. A one-to-one coupling between muscle contractions and transmural PD fluctuations was observed in all animals; ablation of the extrinsic and/or myenteric neurons did not eliminate this correlation. We conclude that, in the rat jejunum, the submucosal plexus alone can integrate the reflex that couples ion secretion to muscle contraction.