Organization of fasting and postprandial myoelectric activity in stomach and duodenum of conscious dogs.

In conscious dogs, contractile and myoelectric activity was recorded from force transducers and monopolar electrodes chronically implanted in the serosal surface of the proximal and distal stomach. Periodic activity during fasting was characterized at each site. Proximally, activity fronts consisted of a series of regular large-amplitude contractions, without correlated myoelectric changes, occurring at 50-s intervals. The distal activity front comprised a series of bursts of two to three contractions 11 s apart, with each burst in phase with a proximal contraction. Only during the burst sequence was each electrical slow wave associated with a spike burst (1:1 phase locking). In contrast, 1:1 phase locking characterized the electrical correlates of the duodenal activity front. Oral feeding abolished periodic activity for at least 3 h. Postprandially, the proximal stomach remained electrically silent; in the duodenum spike bursts were intermittently associated with regular slow waves, but in the distal stomach regular low-amplitude contractions were characterized electrically by 1:1 phase-locked spike bursts and slow waves. These observations suggest that the proximal stomach regulates the canine fasting activity front and require modification of the concept that 1:1 phase locking is a necessary condition of the activity front.