Selective role of vagal and nonvagal innervation in initiation and coordination of gastric and small bowel patterns of interdigestive and postprandial motility

Our previous studies suggested that extrinsic innervation modulates upper g ut motility but is not requisite for cyclic interdigestive and postprandial motility of the stomach. However, the specific role of vagal and nonvagal extrinsic innervation in the initiation, coordination, and pattern of gastr ic motility in dogs after denervation of the entire upper gastrointestinal tract remains unclear. The aim of this study was to determine the role of v agal and nonvagal extrinsic innervation in control of gastric motility patt erns. Mongrel dogs were subjected first to extrinsic denervation (in situ n eural isolation) of the stomach, small bowel, proximal colon, liver, and pa ncreas but specifically maintaining vagal innervation to the stomach alone. After fasting and fed motility patterns were measured with indwelling gast ric and small bowel manometry catheters, the dogs underwent transthoracic t runcal vagotomy (completion of total extrinsic denervation of stomach), and motility studies were repeated. Vagal integrity to the stomach and pancrea s was confirmed by means of a modified Hollander test and serum pancreatic polypeptide concentrations after the injection of exogenous insulin, respec tively. We found that a cyclic motility pattern (migrating motor complex) p ersisted during fasting in both the stomach and the small bowel and that th e patterns of the stomach and the duodenum remained temporally coordinated before and after vagotomy. However, although a cyclic phase III activity pe rsisted in the stomach after vagotomy, the number of contractions and the m otility index during phase III were decreased, and the duration between gro upings of contractions was increased. No differences were noted in the dura tion of postprandial inhibition after feeding meals before and after vagoto my. These observations support our hypothesis that the vagal nerves are not necessary for the initiation or temporal coordination of global fasting or postprandial gastroduodenal motility, patterns but are involved in modulat ing the pattern of contractions during gastric phase III.