Effect of nifedipine on the motility of the sphincter of Oddi and small bowel of the opossum.

The effect of the calcium-channel blocker nifedipine on the electromyographic activity of the small bowel and sphincter of Oddi was studied in conscious opossums. Electromyographic and arterial pressure recordings were started 7-10 days after implantation of seven pairs of electrodes along the small bowel and sphincter of Oddi. Continuous infusion of nifedipine caused a dose-dependent reduction of the frequency of spike bursts in the small bowel and sphincter of Oddi. Nifedipine at high doses abolished the migrating motor complex in the gastrointestinal tract. The frequency of slow waves was unchanged. This drug possibly inhibits the membrane influx of calcium into the smooth muscle cells of the gastrointestinal tract. We conclude that nifedipine causes an intense decrease in the motility of the small bowel and sphincter of Oddi.