CONTRACTION AND ACCOMMODATION OF GUINEA-PIG DUODENUM INVITRO

Because duodenal resistance to gastric emptying depends in part on duodenal capacity, we examined the changes of duodenal diameter, length, and luminal pressure that occur in response to injection of bolus volumes. Filling the duodenum led to a powerful, nonpropagating contraction of the duodenum. After the end of filling, sequential duodenal segments widened and duodenal pressure and length returned to baseline; i.e., there was accommodation. Accommodation was volume dependent and ceased at volumes greater-than-or-equal-to 1.2 ml. The entire duodenum unfolded most immediately and the initial increase of pressure and length was abolished when the duodenal musculature was inhibited by exposure to tetrodotoxin or to Ca2+-free solution. Pressures and pressure accommodation were larger, occurred earlier, and lasted longer when the duodenal musculature was stimulated by exposure to carbachol. Filling of the duodenum from the distal end led to rapid distribution of the bolus through the duodenum and to accommodation similar to that seen with proximal filling. However, phasic duodenal contractions were less powerful on distal than on proximal injection. Spontaneous phasic contractions of the duodenum were accompanied by a similar sequence of changes in duodenal configuration as was observed with filling. We conclude that 1) the duodenum adjusts the tension of its walls at small volumes, and beyond this is fairly rigid; 2) filling the duodenum triggers contraction responses similar to those that occur with spontaneous contractions; and 3) the direction from which the duodenum is filled does not affect its accommodation. We postulate that the filling response of the duodenum may critically affect gastric emptying.