Reflex regulation of flow resistance in the feline sphincter of Oddi by hydrostatic pressure in the biliary tract.

Despite wide variations in bile secretion and biliary tract capacitance, the pressure in the bile ducts is fairly constant. Recent studies have demonstrated that both inhibitory and excitatory nerves regulate the activity of the sphincter of Oddi. In the present study, it was consistently found that the resistance by the choledochoduodenal junction to a constant flow, within the physiologic range of hepatic bile output, is reduced when the hydrostatic pressure in the gallbladder and bile ducts is increased from 0 to 10, 0 to 15, and 0 to 20 cmH2O. This response was eliminated by tetrodotoxin or infiltration of the junction between the common bile duct and the cystic duct by mepivacaine, a local anesthetic. The results suggest a homeostatic mechanism during the interprandial periods, when the activity of the sphincter of Oddi is regulated by the distending pressure in the biliary tract. This reflex regulation is mediated by modulation of the activity of inhibitory nerves running along the common bile duct.