Changes in electrical and mechanical activity during ontogeny of
the canine proximal colon.
Ward, Sean M.
Department of Physiology and Cell Biology, University of Nevada
School of Medicine, Reno, NV 89557, TEL (702) 784-6908, FAX (702)
784-6903, Email: sean@physio.unr.edu
APStracts 3:0024G, 1996.
The ontogenetic development of the circular muscle layer of the canine
proximal colon was studied in animals from midway through gestation
through to 30 days old. With age, there was an increase in RMP along
the submucosal surface and a decrease along the myenteric surface of
the circular layer. Coinciding with the changes in membrane
potential, slow waves increased in amplitude along the submucosal
border and decreased in amplitude along the myenteric border. Muscle
strips from animals midway through gestation were mechanically
quiescent, however 1 week prior to birth spontaneous activity was
observed. Electrical field stimulation of enteric nerves increased
spontaneous contractions, this increase in activity was reversed to
inhibition by atropine. In the presence of atropine and L-NA or L
-NAME a non-cholinergic excitation was revealed at stimulation
frequencies greater than 5 Hz. The results of these studies provide
evidence that the canine proximal colon is spontaneously rhythmic and
a functional innervation to the circular muscle layer exists prior to
birth. The gradient in resting membrane potential across the circular
layer is absent at birth but develops within the first 2-3 weeks
following parturition.
Received 14 August 1995; accepted in final form 1 January 1996.
APS Manuscript Number G351-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96