Tonic activity of submucosal neurons influences basal ion transport.

The influence of tonically active submucosal neurons on basal ion transport was studied using sheets of guinea pig ileum set up in flux chambers. Tetrodotoxin evoked an immediate and sustained decrease in short-circuit current that was sustained for 60 minutes compared with control tissues in which basal currents gradually decreased over time. Time-dependent changes in basal short-circuit currents in tissues treated with atropine were not significantly different from control tissues. The decrease in short-circuit current after tetrodotoxin resulted from a greater increase in net chloride absorption than sodium absorption. Changes in net sodium and chloride transport were due to an increase in the mucosal-to-serosal fluxes of these ions. The results suggest that tonic activity of submucosal neurons limits the absorptive capacity of the guinea pig ileum.