SUMMARYIn four conscious dogs mechanical activity of the gastroduodenal junction was recorded with chronically implanted strain gauge transducers and induction coils. The data were evaluated by a computer. Analog circuits were used in order to reduce the data which were transferred to the computer. In the digestive state the contractions of the pyloric sphincter and duodenal bulb were correlated in such a way that the contractions of the duodenal bulb were inhibited when the gastric waves travelled across the antrum and that the bulb contracted once or twice when the peristaltic waves arrived at the gastroduodenal junction. However, the timing between pyloric and duodenal contractions was imperfect. Contraction maxima of the duodenal bulb often occurred before the pylorus was closed. This was due to the different inherent frequencies of the pyloric and duodenal contractions. In the interdigestive state the timing between the pyloric and duodenal contractions was as imperfect as during the digestive state. In phase III of the interdigestive activity, however, the strong antral contractions were regularly associated with inhibition of the duodenal bulb. This phenomenon can be interpreted as co-ordination between gastric and duodenal activity.

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