EXTRINSIC AND INTRINSIC PATHWAYS CONCERNED WITH INTESTINAL INHIBITION DURING INTESTINAL DISTENTION

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Abstract
Motility of the jejunum above and below a distention was recorded by the use of 2 balloon-Hg-manometer systems in expts. on unmedicated dogs having 1 or 2 Thiry or Thiry-Vella fistulae. Denervations were done to permit separate evaluation of the role of intrinsic and extrinsic pathways in the responses observed. Distention of the jejunum of the dog results in inhibition of all types of movement and decreased tonus of the undistended part of the jejunum in both directions from the site of distention. The degree of inhibition depends upon the rapidity with which the pressure is increased in the balloon and upon the final pressure attained. The inhibition of the normal jejunum as a result of distention is accomplished primarily by means of reflexes over the extrinsic nerves. The jejunum contains afferent endings which are stimulated during distention and efferent nerve endings which have an adrenine-like effect on the motor functions of the jejunum. When the extrinsic nerves are cut an intrinsic and less efficient mechanism for mediating intestinal inhibition during intestinal distention is unmasked. This pathway is presumably over the intrinsic nerve cells of the intestinal wall. When the extrinsic nerves are intact inhibition of the intestine during distention is accomplished as well in the absence of the intrinsic connections as when they are present.

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