AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 3 484-G491, Copyright © 1990 by American Physiological Society
Electrical and mechanical interactions between the muscle layers of canine proximal colon
P. J. Sabourin, Y. J. Kingma and K. L. Bowes
Surgical/Medical Research Institute, University of Alberta, Edmonton, Canada.
Electrical and mechanical interactions between the two smooth muscle layers
of canine colon have been studied using a dual sucrose gap apparatus.
Muscle samples were dissected into an L-shape, with one leg cut in the
circular direction and the other cut in the longitudinal direction.
Longitudinal muscle was removed from the circular leg and circular muscle
was removed from the longitudinal leg. The bend of the L contained both
layers. The activity of the two layers was studied simultaneously under
basal conditions, after stimulation by neostigmine and carbachol, and in
the presence of tetrodotoxin. Interactions were more common after
stimulation and were marked by modification of one layer's mechanical and
electrical activity during increased activity in the other layer. Two
patterns were commonly observed. First, during a burst of membrane
potential oscillations and spike potentials in the longitudinal layer, slow
waves in the circular layer developed spike potentials and some slow waves
were also prolonged. Second, during a slow-wave cycle in the circular
layer, the amplitude of membrane potential oscillations in the longitudinal
layer was increased with an associated increase in the incidence of spike
potentials. These interactions were associated with contractions of
increased strength, which were similar in both layers. All interactions
continued after nerve-conduction blockade by tetrodotoxin.
