Relationships between pressure and flow across the gastroduodenal junction in dogs.

Antroduodenal pressure events were measured simultaneously with transpyloric flow, in conscious dogs, to evaluate the role of mechanical factors modulating this flow. The relationships between pressure and flow across the gastroduodenal junction were never linear. During the interdigestive state, terminal antral contraction occurred 0.9 +/- 0.29 s after the onset of the gush of gastric contents. Hence, the highest flow rate occurred during the period of lowest resistance. After a meal, terminal antral contraction began 3.3 +/- 0.87 s before the flow of chyme, and resistance rose simultaneously with flow rate. The antroduodenal resistance was 10 times higher than during the interdigestive state (8.33 +/- 1.56 vs. 0.73 +/- 0.34 mmHg.ml-1.s). The pyloroduodenal resistance was always lower than the antropyloric one. It is concluded that, because of the temporal relationship between motor events and flow, pure resistive behavior of the junction occurred only after a meal.