Character and cholinergic control of myoelectric activity in ovine duodenal bulb: relationships to adjacent regions

The distinctive motor activity of duodenal bulb is incompletely understood. Thus, in six conscious sheep the myoelectric activity of pyloric antrum, duodenal bulb and distal duodenum were continuously recorded in order to assess the myoelectric patterns of duodenal bulb and the relationships to adjacent regions before and after feeding or cholinergic drug administration. It was found that in duodenal bulb slow waves are not always absent. Two main types of the spike burst, of high and low amplitude, were detected. Duration of bulbar spike bursts was shorter than in pyloric antrum and longer than in distal duodenum. Unlike in pyloric antrum and distal duodenum these spike bursts arrived in duodenal bulb at irregular intervals. They participated in the formation of phases of migrating myoelectric complex, minute rhythm and feed pattern. Cholinergic antagonists completely blocked these spike bursts in duodenal bulb and in distal duodenum, but not in pyloric antrum. Low amplitude spike bursts arrived occasionally, and they were not inhibited by atropine administration. They were not observed following hexamethonium administration. It is concluded that the character of myoelectric activity in ovine duodenal bulb is distinct from that in pyloric antrum and distal duodenum and remaining partially independent, is fairly well correlated with neighbouring regions.