AJP - Cell Physiology, Vol 256, Issue 3 C466-C477, Copyright © 1989 by American Physiological Society

ARTICLES

Electrical pacemakers of canine proximal colon are functionally innervated by inhibitory motor neurons

T. K. Smith, J. B. Reed and K. M. Sanders
Department of Physiology, University of Nevada School of Medicine, Reno 89431.

Pacemaker activity in the canine proximal colon occurs at the submucosal and myenteric borders of the circular layer [Am. J. Physiol. 252 (Cell Physiol. 21): C215-C224 and C290-C299, 1987]. The present study investigated the neural regulation of rhythmic electrical activity. Spontaneous inhibitory junction potentials (IJPs) were observed in intracellular recordings from circular muscle cells near the myenteric border. The amplitudes of these events decayed with distance through the circular layer. Stimulation at the myenteric plexus surface evoked IJPs that mimicked the spontaneous events. Stimulation at the submucosal surface evoked IJPs in adjacent cells that were of shorter duration and of different waveform than myenteric IJPs. Amplitudes of IJPs evoked by stimulation near either surface decayed with distance from the site of stimulation. The decay functions for IJPs were essentially identical to the decay of spontaneous slow waves or myenteric potential oscillations. Spontaneous and evoked IJPs affected the amplitudes, durations, and patterns of ongoing rhythmic electrical activity. The data suggest that myenteric and submucosal pacemaker populations may be innervated by different populations of inhibitory nerve fibers. Innervation appears to be heterogeneous with dense populations of inhibitory nerve fibers predominantly located in the pacemaker regions. Neural regulations of pacemaker activity influences rhythmic electrical activity throughout the muscularis.

This article has been cited by other articles:

				L. Sha, G. Farrugia, W. S. Harmsen, and J. H. Szurszewski Membrane potential gradient is carbon monoxide-dependent in mouse and human small intestine Am J Physiol Gastrointest Liver Physiol, August 1, 2007; 293(2): G438 - G445. [Abstract] [Full Text] [PDF]

				R. M. Gwynne and J. C. Bornstein Mechanisms underlying nutrient-induced segmentation in isolated guinea pig small intestine Am J Physiol Gastrointest Liver Physiol, April 1, 2007; 292(4): G1162 - G1172. [Abstract] [Full Text] [PDF]

				N. J. Spencer, G. W. Hennig, and T. K. Smith Electrical rhythmicity and spread of action potentials in longitudinal muscle of guinea pig distal colon Am J Physiol Gastrointest Liver Physiol, May 1, 2002; 282(5): G904 - G917. [Abstract] [Full Text] [PDF]

				S M Ward Interstitial cells of Cajal in enteric neurotransmission Gut, December 1, 2000; 47(90004): iv40 - 43. [Full Text] [PDF]

				S. D. Koh, G. M. Dick, and K. M. Sanders Small-conductance Ca2+-dependent K+ channels activated by ATP in murine colonic smooth muscle Am J Physiol Cell Physiol, December 1, 1997; 273(6): C2010 - C2021. [Abstract] [Full Text] [PDF]