Action potentials in gastrointestinal smooth muscle

1991 ◽  
Vol 69 (8) ◽  
pp. 1133-1142 ◽  
Author(s):  
Jan D. Huizinga
Keyword(s):  
Smooth Muscle ◽  
Slow Wave ◽  
Action Potentials ◽  
Interstitial Cells Of Cajal ◽  
Cell Structure ◽  
Interstitial Cells ◽  
Research Progress ◽  
Wave Type ◽  
Gastrointestinal Smooth Muscle ◽  
Cells Of Cajal

Recent investigation of the ultrastracture and electrophysiology of gastrointestinal smooth muscle layers has revealed a fascinating heterogeneity in cell type, cell structure, intercellular communication, and generated electrical activities. Networks of interstitial cells of Cajal (ICC) have been identified in many muscle layers and evidence is accumulating for a role of these networks in gut pacemaking activity. Synchronized motility in the organs of the gut result from interaction between ICC, neural-tissue, and smooth muscle cells. Regulation of cell to cell communication between the different cell types will be an important area for further research. Progress has been made in the elucidation of the ionic basis of the slow wave type action potentials and the spike-like action potentials. The mechanism underlying smooth muscle autorhythmicity seems different from that encountered in cardiac tissue, and evidence exists for metabolic regulation of the frequency of slow wave type action potentials.Key words: pacemaker activity, slow wave, autorhythmicity, interstitial cells of Cajal.

Inhibitory innervation of colonic smooth muscle cells and interstitial cells of Cajal

1990 ◽  
Vol 68 (3) ◽  
pp. 447-454 ◽  
Author(s):  
Jan D. Huizinga ◽  
Irene Berezin ◽  
Edwin E. Daniel ◽  
Edwin Chow
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Action Potentials ◽  
Interstitial Cells Of Cajal ◽  
Reversal Potential ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Interstitial Cells ◽  
Equilibrium Potential ◽  
Cells Of Cajal

The effect of neural inhibition on the electrical activities of circular and longitudinal colonic smooth muscle was investigated. In addition, a comparative study was carried out between circular muscle preparations with and without the "submucosal" and "myenteric plexus" network of interstitial cells of Cajal (ICC) to study innervation of the "submucosal" ICC and to investigate whether or not the ICC network is an essential intermediary system for inhibitory innervation of smooth muscle cells. Electrical stimulation of intrinsic nerves in the presence of atropine caused inhibitory junction potentials (ijps) throughout the circular and longitudinal muscle layers. The ijp amplitude depended on the membrane potential and not on the location of the muscle cells with respect to the ICC network. Neurally mediated inhibition of the colon resulted in a reduction in amplitude and duration of slow wave type action potentials in circular and abolishment of spike-like action potentials in longitudinal smooth muscle, both resulting in a reduction of contractile activity. With respect to mediation by ICC, the study shows (i) "submucosal" ICC receive direct inhibitory innervation and (ii) circular smooth muscle cells can be directly innervated by inhibitory nerves without ICC as necessary intermediaries. The reversal potential of the ijp in colonic smooth muscle was observed to be approximately −76 mV, close to the estimated potassium equilibrium potential, suggesting that the nerve-mediated hyperpolarization is caused by increased potassium conductance.Key words: enteric nerves, potassium conductance, pacemaker activity, VIP, inhibitory junction potential.

Ultrastructure of interstitial cells of Cajal in the canine distal esophagus

1994 ◽  
Vol 72 (9) ◽  
pp. 1049-1059 ◽  
Author(s):  
I. Berezin ◽  
E. E. Daniel ◽  
J. D. Huizinga
Keyword(s):  
Smooth Muscle ◽  
Action Potentials ◽  
Neural Control ◽  
Interstitial Cells Of Cajal ◽  
Three Dimensional ◽  
Muscle Layer ◽  
Interstitial Cells ◽  
Distal Esophagus ◽  
Esophageal Sphincter ◽  
Cells Of Cajal

The ultrastructure of canine distal esophagus was studied focusing on interstitial cells of Cajal (ICC) and their relationships to nerves and muscle. The distal esophagus consisted of two muscle layers composed of intertwining skeletal and smooth muscle bundles. The ICC formed an interconnecting network and were an integral part of these structures. The ICC communicated with one another and with adjacent smooth muscle cells through numerous gap junctions. The morphology of individual ICC resembled that observed in other gut regions. All interstitial cells were densely innervated. The highest density of ICC, just proximal to the lower esophageal sphincter, coincided with the previously reported highest incidence of occurrence of electrical slow wave type action potentials. Examination of a large number of structural associations of ICC led us to conclude that in the distal esophagus, two networks of ICC and nerves exist, one associated with the inner muscle layer, another associated with the outer muscle layer. These networks are not sheet-like structures, such as the network of ICC in the myenteric plexus or deep muscular plexus of the small intestine, but are three dimensional and are interspersed throughout both muscle layers. The networks do not extend into Auerbach's plexus. The main branches of the networks run along the long axis of the esophagus and seem ideally suited to facilitate communication in this direction. These observations suggest that esophageal interstitial cells are structurally organized in such a manner that they may play a role in pacemaking and neural control of esophageal motility.Key words: interstitial cells of Cajal, enteric nervous system, esophagus, ultrastructure, pacemaking.

scholarly journals Regulation of Gastrointestinal Smooth Muscle Function by Interstitial Cells

Physiology ◽  
2016 ◽  
Vol 31 (5) ◽  
pp. 316-326 ◽  
Author(s):  
Kenton M. Sanders ◽  
Yoshihiko Kito ◽  
Sung Jin Hwang ◽  
Sean M. Ward
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Function ◽  
Interstitial Cells Of Cajal ◽  
Smooth Muscles ◽  
Interstitial Cells ◽  
Gastrointestinal Smooth Muscle ◽  
Smooth Muscle Function ◽  
Cells Of Cajal ◽  
Regulatory Functions

Interstitial cells of mesenchymal origin form gap junctions with smooth muscle cells in visceral smooth muscles and provide important regulatory functions. In gastrointestinal (GI) muscles, there are two distinct classes of interstitial cells, c-Kit+interstitial cells of Cajal and PDGFRα+cells, that regulate motility patterns. Loss of these cells may contribute to symptoms in GI motility disorders.

Slow-wave activity in colon: role of network of submucosal interstitial cells of Cajal

1991 ◽  
Vol 260 (4) ◽  
pp. G636-G645 ◽  
Author(s):  
R. Serio ◽  
C. Barajas-Lopez ◽  
E. E. Daniel ◽  
I. Berezin ◽  
J. D. Huizinga
Keyword(s):  
Smooth Muscle ◽  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Circular Muscle ◽  
Interstitial Cells ◽  
Wave Activity ◽  
Slow Waves ◽  
Slow Wave Activity ◽  
Plateau Potentials ◽  
Cells Of Cajal

The present study compares the electrophysiological properties of two preparations dissected from the canine colon circular muscle layer: first, containing the submucosal network of interstitial cells of Cajal (ICC) with two to four associated smooth muscle cell layers, and second, a circular muscle preparation devoid of the submucosal ICC network. In the ICC-rich preparations, consistent slow-wave activity was observed with prolonged plateau potentials of approximately 10-s duration. The plateau potentials were sensitive to D 600. In approximately 45% of circular muscle preparations devoid of the submucosal ICC network (confirmed using electron microscopy) slow waves, of different waveshape, were recorded at frequencies identical to those in whole circular muscle preparations. These slow waves did not show a plateau potential. Compared with ICC-rich preparations with a resting membrane potential of about -80 mV, circular muscle preparations had lower membrane potentials, about -70 mV when active, and about -60 mV when quiescent. Heptanol (1 mM) electrically uncoupled cells, since it abolished electrotonic current spread and allowed measurement of the input resistance by intracellular current injection. Heptanol also affected ionic conductances. Heptanol abolished slow waves; the underlying mechanism needs further investigation. In the presence of heptanol, cells in the isolated ICC network and in circular smooth muscle preparations showed spontaneous hyperpolarizing potential fluctuations at a frequency of four to six per second. These oscillations were abolished by current-induced hyperpolarization and TEA (30 mM) and are therefore likely due to spontaneously active K+ conductance.

Pathways of slow-wave propagation in proximal colon of cats

1990 ◽  
Vol 258 (6) ◽  
pp. G894-G903 ◽  
Author(s):  
J. L. Conklin ◽  
C. Du
Keyword(s):  
Wave Propagation ◽  
Smooth Muscle ◽  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Muscularis Propria ◽  
Interstitial Cells ◽  
Proximal Colon ◽  
Slow Waves ◽  
Cells Of Cajal ◽  
Circular Axis

Colonic slow waves (SWs) are generated by nonneuronal cells located at the interface of the submucosa and muscularis propria. It has been proposed that SWs arise from a complex of nerves, interstitial cells of Cajal, and smooth muscle found at this location. These experiments test the hypothesis that the propagation of colonic SWs depends on an intact interface between the submucosa and muscularis propria. The electromyogram was recorded from segments of the proximal colon of the cat. All intact tissues generated SWs that propagated in the long and circumferential axes of the colon. Tetrodotoxin did not disrupt SW propagation in either axis. Transection of tissues between recording sites interrupted the spread of SWs in both axes. Transection of the submucosa disrupted the longitudinal spread of SWs, whereas transection of the muscularis propria did not. Removing the submucosa from the midportion of tissue segments oriented in the long axis of the colon resulted in a loss of SWs from the segment devoid of submucosa. Transection of the submucosa of tissue segments oriented in the circular axis of the colon did not disrupt circumferential propagation of SWs. Dissecting a 1-cm-wide segment of submucosa from the midportion of such a circularly oriented tissue did not disrupt the circumferential spread of SWs, and SWs were recorded from the muscle segment that was devoid of submucosa. SWs were not recorded from the segment devoid of submucosa when it was isolated from adjacent intact segments. The data support the hypothesis that the regeneration of SWs during their longitudinal propagation takes place at the interface between the submucosa and muscularis propria.

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