A new method for correlating pancreatic and biliary duct pressures and sphincter of Oddi electromyography.

Myoelectric activity of the sphincter of Oddi and duodenum was correlated with pancreatic and biliary duct pressures in eight opossums, in both the fasted and fed states. Four bipolar electrode pairs were implanted in the sphincter of Oddi and duodenum. A polyethylene T tube was placed in the pancreatic duct. The common duct was cannulated through a small bile duct. This method allowed pressure recording for several weeks and avoided interference with the flow of bile or pancreatic juice into the duodenum. The frequency of slow waves was the same in the sphincter of Oddi and duodenum (19 per minute). The variation in the frequency of spike potentials in the sphincter of Oddi correlated to that of the migrating myoelectric complex in the duodenum. The average frequency of slow waves that have superimposed spike potentials in the sphincter of Oddi and duodenum was 3.0 and 0 in phase 1, 4.7, and 6.2 in phase II, 6.1 and 15.1 in phase III, and 3.4 and 6.3 in phase IV, respectively. The average duration of a migrating myoelectric complex cycle was 92 minutes. After feeding, the interdigestive phases of the migrating myoelectric complex were abolished and substituted by a feeding activity pattern that was characterized by an average number of sphincter of Oddi and duodenum spikes of 6.6 and 10.7, respectively. The mean fasting pressure in the pancreatic and biliary duct was 15 and 13 mmHg, respectively. Pressure changes were of two types--synchronous with respiratory movements and with each sphincter of Oddi spike potential. There was no variation in the baseline pressure during the migrating myoelectric complex phases and the fed state. It is concluded that the sphincter of Oddi of the fasting opossum exhibits cyclic changes in the number of spike potentials that correlate with the migrating myoelectric complex in the duodenum. However, the number and amplitude of spike potentials are different in the sphincter of Oddi and duodenum. There is no change in the baseline pressure during fasting and feeding states, and a temporary pressure elevation synchronic with each sphincter of Oddi spike potential was observed.