THE ROLE OF EXTRINSIC NERVOUS-SYSTEM IN JEJUNAL-ABSORPTION DURING ELEVATION OF INTRALUMINAL PRESSURE IN ANESTHETIZED DOGS

The aim of this study was to investigate the role of the extrinsic ner vous system in jejunal absorption under elevated intraluminal pressure of the jejunum. Increase in intraluminal pressure from 0 to 70-100 mm Hg decreased net absorption of fluid, Na+ and Cl-, from 7.6 +/- 0.5 to 5.6 +/- 0.3 ml/15 min, 1.1 +/- 0.1 to 0.7 +/- 0.1 mEq/15 min, and 1.2 +/- 0.1 to 0.8 +/- 0.1 mEq/15 min, respectively. To examine the role of the extrinsic nervous system in the depressed net jejunal absorptio n induced by the increase in intraluminal pressure, jejunal afferent a nd efferent nerve activities were measured in response to the increase in intraluminal pressure. Both afferent and efferent nerve activities increased to 224 +/- 14 and 236 +/- 18% in response to the increase i n intraluminal pressure. In the extrinsic denervated jejunal loop, the responses of net absorption to the elevation of intraluminal pressure were quite different from those in innervated jejunum. That is, in th e denervated jejunal loop the elevation of intraluminal pressure conve rted jejunal absorption to jejunal secretion. These results indicate t hat elevation of intraluminal pressure elicits the jejuno-jejunal refl ex, and this mechanism counteracts jejunal secretion.