AJP - Gastrointestinal and Liver Physiology, Vol 264, Issue 2 341-G350, Copyright © 1993 by American Physiological Society
Intestinal distension alters vagal efferent activity and small intestinal transport in vivo
X. Chu, X. Zhang, W. E. Renehan, W. H. Beierwaltes and R. Fogel
Department of Medicine, Henry Ford Hospital, Detroit, Michigan 48202.
We investigated whether intestinal distension altered net water absorption
by an adjacent noncontiguous segment of intestine and the mechanism for
this effect. Influx and efflux catheters were placed in two intestinal
loops, after which the bowel was transected between the loops. During
perfusion with Ringers-HCO3-, the proximal loop efflux catheter was
elevated 5, 10, or 15 cm above the plane of the rat. Net water absorption
was measured in the nondistended caudal (control) loop. Elevation of the
proximal loop efflux catheter caused distension and increased intraluminal
pressure in this loop but did not alter the circumference or intraluminal
pressure of the caudal loop. Distension increased net water absorption by
the caudal loop if the vagi were intact and the splanchnic nerves
transected. Afferent vagotomy prevented the distension effect. Using the
intracellular recording technique, we were able to show that the increase
in absorption resulted from a reduction in the activity of vagal neurons
innervating the gastrointestinal tract. Intestinal distension reduced the
neural activity of 24 of 26 vagal efferent neurons. Our results demonstrate
that after splanchnectomy intestinal distension activates a neural circuit
that includes afferent and efferent vagal fibers, resulting in increased
water absorption.
