Effect of a Previous Distention of the Intestine on Reflex Inhibition of Gastric Motility.

Abstract

In studying the nerve pathways involved in the reflex inhibition of hunger contractions by distention of a Thiry fistula loop in the dog, it was noticed that a previous long-continued distention of the loop brought about a lower threshold for the reflex. In the experiments here reported, five animals were prepared with Thiry fistulae in the usual manner, the loops being 15-20 cm. long and taken from the upper ileum. After complete recovery the dogs were trained to swallow a stomach tube and to lie quietly on the table without any restraint. Gastric movements were recorded by the customary balloon-tambour method. The intestinal loops were distended by air inflation of a thin-walled balloon which was over-size relative to the lumen of the gut. The balloon was tied over a glass rod so that the expansion would be entirely lateral and the pressure readings would closely approximate the pressure actually applied to the intestinal wall. All records were made after a fasting period of 18-24 hours. In testing for inhibition of gastric motility the intestinal loops were inflated for a short period, usually 10-30 seconds. In sensitizing or reinforcing the reflex, the loops were subjected to a continuous pressure of 75 mm. Hg. for 24 hours, following which tests were again made. The essential results may be seen in Table I and Fig. 1. In the control experiments pressures in the loops of 75 to 120 mm. Hg. produced inhibition of gastric movement in 25 out of 55 tests. Each dog responded about half the time, the percentage of responses increasing somewhat with the higher pressures. It was noted that hunger contractions of type 2 were most easily affected. Often there was a marked lowering of tonus with the presence of smaller contractions at this lower level.