Motor Activity and Transit in the Autonomically Denervated Jejunum

The role of extrinsic (autonomic) innervation in postprandial contractile activity of the small intestine is unknown. Using a canine model, we investigated the effects of complete extrinsic denervation on the parameters of fasting and postprandial jejunal contractions and their relationship to intestinal transit. Individual contractions were recorded using strain gauge transducers. Spatial and temporal parameters of contractions were analyzed by computer methods. Bolus injection of 14C-polyethylene glycol was used to calculate intestinal transit rates. Statistical comparisons of control and denervated animals were made by nonparametric tests. Extrinsic denervation did not abolish fasting or fed motor activity, but the following effects were observed: (1) the frequency of migrating motor complexes (MMCs) increased; (2) the onset of fed motor activity was delayed, and the duration of fed activity was shortened; (3) frequency, mean amplitude, and mean area of postprandial contractions were decreased; (4) fewer contractions propagated distally, and mean propagation distance was shortened; and (5) intestinal transit was slower for solids, but not for liquids. In the small intestine, extrinsic nerves modulate motor activity, which is under primary control of the intrinsic (enteric) nervous system.