AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 3 690-R698, Copyright © 1995 by American Physiological Society
Effect of salt and water balance on colonic motility of white leghorn roosters
M. Brummermann and E. J. Braun
Department of Physiology, University of Arizona, Tucson 85724.
The motility of the lower gastrointestinal (GI) tract of white leghorn
roosters was observed by radiographic methods. Intracolonic pressure
changes were recorded, and the mechanical activity of the colon was
quantified using strain gauges that were attached to the serosa. Two types
of retrograde contraction waves were observed: small fast peristaltic
contractions (15 min-1) and large slow contractions. The small fast
contractions are the actual vehicle of the retrograde movement, but they
seemed to be linked to respiratory movements in the fashion of coupled
oscillators during most of their activity time (94%). This makes them an
unlikely target for regulation. The large slow waves (3 min-1) probably
reflect contractions of the longitudinal musculature. They are retrograde
and may permit or modulate the refluxing of urine. The effects of water
deprivation, intravenous volume, and salt loads on colonic motility were
analyzed. All manipulations that increased urine flow rates without
changing urine osmolality resulted in increased propagation speed of the
large contraction waves. All manipulations that increased urine osmolality
resulted in decreases in activity time of the large-wave pattern. These
results suggest a hydration state-related control of the retrograde colonic
motility in birds. Direct stimulation of central osmoreceptors had no such
effects, indicating that local volume and osmolality receptors of the
cloaca are more important than central receptors for this adjustment of
colonic motility.
