A slow wave frequency complex of the canine small intestine during the fasting state.

The electrical activity of the duodenum and proximal jejunum was studied in conscious healthy dogs implanted with unipolar silver electrodes. A computerized method was used for the calculation of the mean frequency of the slow wave for each consecutive minute of the electromyographic signal. A "slow wave frequency complex" was identified in the fasted animals. It was characterized by an increase of the mean frequency of the slow wave which ranged, from one dog to another, between 1 and 3 cycles/min. The complex lasted about 30 min. It consisted of two distinct phases: a phase of increasing frequency of the slow wave which lasted about one-third of the total duration of the complex and a phase of progressive return of the frequency to its precomplex value. Each phase III of the migrating myoelectric complex occurring in both the duodenum and the jejunum was associated with one slow wave frequency complex. The phase III began a few minutes before the start of the slow wave frequency complex and ended a few minutes before the slow wave frequency reached its maximum. Ectopic phase IIIs which occurred in the jejunum but not in the duodenum were not associated with slow wave frequency complexes. The slow wave frequency complex was never seen in the fed dogs.