Background. Several neural and hormonal factors are known to affect the motility of the sphincter of Oddi. However, the precise mechanisms of the control of sphincter motility have not been completely explored. We investigated the relationship of canine biliary sphincter motility when it is extrinsically denervated by neural isolation of the pancreatoduodenal region. Methods. Interdigestive and postprandial sphincter motility in a denervated pancreatoduodenal segment and effects of cholecystokinin-octapeptide were studied in 7 conscious dogs. Data were compared with those of 7 neurally intact control dogs. Results. After extrinsic denervation of the pancreatoduodenal, region, sphincter motility exerted a cyclic change in concert with the duodenal myoelectric cycles; this change involved short cyclic bursts of motor activity, which gradually increased in intensity. The increase in the cyclic bursts of motor activity was also cyclic and associated with an increase in the plasma motilin concentration. Neural isolation of the pancreatoduodenal region increased sphincter basal pressure and motility index (integral per minute). In the denervated biliary sphincter, the feeding pattern and temporary inhibitory effect of feeding, as seen in controls, were absent, which suggests the role of extrinsic nerves in delivering bile into the duodenum after feeding. In the denervated dogs, cholecystokinin-octapeptide caused excitation of the sphincter activity, instead of relaxation observed in controls. Conclusions. Extrinsic innervation to the pancreatoduodenal region has an inhibitory effect on biliary sphincter motility. Abnormalities in extrinsic innervation to the biliary sphincter might increase the resistance of the sphincter to the bile flow and induce bile stagnation.
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