A novel in vitro technique to study extrinsic neural control of rabbit colonic muscle and epithelial function

A novel in vitro technique capable of simultaneously measuring distal colonic epithelial potential difference and muscle contraction is described. Under basal conditions, oscillations in both muscle tone and potential difference were observed. Pelvic nerve stimulation was shown to evoke strong "duration" contractile responses in both the longitudinal and circular muscle layers. Additionally, tonic changes in potential difference extending beyond the train of stimuli were observed, suggesting for the first time that colonic ion transport may be influenced by the pelvic nerves. However, it was unclear whether these were direct effects or indirect actions resulting from muscle contractions causing mechanical stimulation of nerves of the submucosal plexus. Lumbar colonic nerve stimulation inhibited spontaneous contractile activity and reduced basal tone in both muscle layers. However, there was no consistent effect of sympathetic nerve stimulation on transepithelial potential difference. Each of the muscle and epithelial effects of sympathetic nerve stimulation was mimicked by exogenous norepinephrine. Based on these data, it is concluded that colonic function is strongly influenced by the extrinsic innervation. Furthermore, relatively long-term modulation of epithelial function can be achieved by short bursts of pelvic nerve activity.