Mechanism of pyloric contraction and relaxation after pylorus preserving gastrectomy

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Our study aimed at (1)measuring pyloric relaxation correctly and (2)determining the role of the intrinsic and extrinsic neural pathway in pyloric relaxation. Second aim of this study is to examine gastropyloric motility after pylorus-preserving gastrectomy (PPG) and to determine the influence of the pyloric branch of the vagus nerve. (Methods) Seven groups of dogs were used : five dogs had an intact gastrointestinal tract (control group) ; five dogs had transection and re-anastomosis of the antrum 3cm proximal to the pylorus (antral transection group) ; five dogs had extrinsic pyloric denervation (denervation group) ; five dogs had transection and re-anastomosis of the antrum with extrinsic pyloric ring denervation (transection with denervation group) ; five dogs had truncal vagotomy (vagotomy group) ; five dogs had PPG with preservation of the pyloric branch of the vagus (PPPG) ; and five dogs had PPG with resection of the pyloric branch of the vagus (RPPG). Gastropyloroduodenal motility was recorded by a strain-gauge force transducer in conscious dogs. (Results) In the control and denervation groups, pyloric relaxation was observed only during phase III of the interdigestive migrating motor complex. In the antral transection, transection with denervation, and vagotomy groups, pyloric relaxation was not observed in either the interdigestive or the postprandial state. The frequency of pyloric contractions increased in these groups in comparison with the control group. No significant differences were found between PPPG and RPPG in gastropyloroduodenal motility during either the interdigestive or postprandial state. (Conclusion) Results suggest that pyloric relaxation occurred during phase III to expel undigested particles from the stomach and that descending antral intramural pathways play an important role in the control of pyloric relaxation. Furthermore, it is not necessary to preserve the pyloric branch of the vagus for gastropyloroduodenal motility after PPG.