Pathways of slow-wave propagation in proximal colon of cats

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

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1991.260.4.g636 ◽

1991 ◽

Vol 260 (4) ◽

pp. G636-G645 ◽

Cited By ~ 4

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.

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Action potentials in gastrointestinal smooth muscle

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y91-166 ◽

1991 ◽

Vol 69 (8) ◽

pp. 1133-1142 ◽

Cited By ~ 18

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.

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Selective lesioning of interstitial cells of Cajal by methylene blue and light leads to loss of slow waves

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1994.266.3.g485 ◽

1994 ◽

Vol 266 (3) ◽

pp. G485-G496 ◽

Cited By ~ 15

Author(s):

L. W. Liu ◽

L. Thuneberg ◽

J. D. Huizinga

Keyword(s):

Methylene Blue ◽

Smooth Muscle ◽

Smooth Muscle Cells ◽

Electrical Activity ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Wave Activity ◽

Slow Waves ◽

Slow Wave Activity ◽

Cells Of Cajal

Incubation with 50 microM methylene blue (MB) and subsequent intense illumination resulted in abolition of the slow-wave activity in the submuscular interstitial cells of Cajal-circular muscle (ICC-CM) preparations of canine colon. This was often accompanied by a decrease in resting membrane potential. Repolarization of cells back to -70 mV did not restore the slow-wave activity, indicating that MB plus light directly interrupted the generation mechanism of slow waves. After MB incubation, a 2-min illumination consistently changed the mitochondrial conformation in ICCs from very condensed to orthodox, without inducing any obvious changes in smooth muscle cells. After 4- to 10-min illumination, ICCs became progressively more damaged with swollen and ruptured mitochondria, loss of cytoplasmic contrast and detail, loss of caveolae, and rupture of the plasma membrane. No damage was seen in smooth muscle cells or nerves. Gap junctional ultrastructure was preserved. Intense illumination without preincubation with MB left the slow waves and the ultrastructure of ICC-CM preparations unaffected. In CM preparations, without the submuscular ICC-smooth-muscle network, MB plus light induced no changes in electrical activity. We conclude that the correlation between selective damage to the submuscular ICCs (relative to smooth muscle) and selective loss of the slow-wave activity (relative to other electrical activity of the CM) strongly indicates that the ICCs play an essential role in the generation of slow waves.

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Conditional genetic deletion of Ano1 in interstitial cells of Cajal impairs Ca2+ transients and slow waves in adult mouse small intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00363.2016 ◽

2017 ◽

Vol 312 (3) ◽

pp. G228-G245 ◽

Cited By ~ 36

Author(s):

John Malysz ◽

Simon J. Gibbons ◽

Siva A. Saravanaperumal ◽

Peng Du ◽

Seth T. Eisenman ◽

...

Keyword(s):

Small Intestine ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Adult Mouse ◽

Rank Order ◽

Interstitial Cells ◽

Slow Waves ◽

Functional Reserve ◽

Mouse Small Intestine ◽

Cells Of Cajal

Myenteric plexus interstitial cells of Cajal (ICC-MY) in the small intestine are Kit+ electrical pacemakers that express the Ano1/TMEM16A Ca2+-activated Cl– channel, whose functions in the gastrointestinal tract remain incompletely understood. In this study, an inducible Cre-LoxP-based approach was used to advance the understanding of Ano1 in ICC-MY of adult mouse small intestine. KitCreERT2/+;Ano1Fl/Fl mice were treated with tamoxifen or vehicle, and small intestines (mucosa free) were examined. Quantitative RT-PCR demonstrated ~50% reduction in Ano1 mRNA in intestines of conditional knockouts (cKOs) compared with vehicle-treated controls. Whole mount immunohistochemistry showed a mosaic/patchy pattern loss of Ano1 protein in ICC networks. Ca2+ transients in ICC-MY network of cKOs displayed reduced duration compared with highly synchronized controls and showed synchronized and desynchronized profiles. When matched, the rank order for Ano1 expression in Ca2+ signal imaged fields of view was as follows: vehicle controls>>>cKO(synchronized)>cKO(desynchronized). Maintenance of Ca2+ transients’ synchronicity despite high loss of Ano1 indicates a large functional reserve of Ano1 in the ICC-MY network. Slow waves in cKOs displayed reduced duration and increased inter-slow-wave interval and occurred in regular- and irregular-amplitude oscillating patterns. The latter activity suggested ongoing interaction by independent interacting oscillators. Lack of slow waves and depolarization, previously reported for neonatal constitutive knockouts, were also seen. In summary, Ano1 in adults regulates gastrointestinal function by determining Ca2+ transients and electrical activity depending on the level of Ano1 expression. Partial Ano1 loss results in Ca2+ transients and slow waves displaying reduced duration, while complete and widespread absence of Ano1 in ICC-MY causes lack of slow wave and desynchronized Ca2+ transients. NEW & NOTEWORTHY The Ca2+-activated Cl− channel, Ano1, in interstitial cells of Cajal (ICC) is necessary for normal gastrointestinal motility. We knocked out Ano1 to varying degrees in ICC of adult mice. Partial knockout of Ano1 shortened the widths of electrical slow waves and Ca2+ transients in myenteric ICC but Ca2+ transient synchronicity was preserved. Near-complete knockout was necessary for transient desynchronization and loss of slow waves, indicating a large functional reserve of Ano1 in ICC. View this article's corresponding video summary at https://youtu.be/cyPtDP0KLY4 .

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Na+-K+-Cl− cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00277.2016 ◽

2016 ◽

Vol 311 (6) ◽

pp. G1037-G1046 ◽

Cited By ~ 10

Author(s):

Mei Hong Zhu ◽

Tae Sik Sung ◽

Masaaki Kurahashi ◽

Lauren E. O'Kane ◽

Kate O'Driscoll ◽

...

Keyword(s):

Slow Wave ◽

Interstitial Cells Of Cajal ◽

High Current Density ◽

Reversal Potential ◽

Interstitial Cells ◽

Slow Waves ◽

Hek293 Cells ◽

Pacemaker Activity ◽

Inward Currents ◽

Cells Of Cajal

Interstitial cells of Cajal (ICC) generate electrical slow waves by coordinated openings of ANO1 channels, a Ca2+-activated Cl− (CaCC) conductance. Efflux of Cl− during slow waves must be significant, as there is high current density during slow-wave currents and slow waves are of sufficient magnitude to depolarize the syncytium of smooth muscle cells and PDGFRα+ cells to which they are electrically coupled. We investigated how the driving force for Cl− current is maintained in ICC. We found robust expression of Slc12a2 (which encodes an Na+-K+-Cl− cotransporter, NKCC1) and immunohistochemical confirmation that NKCC1 is expressed in ICC. With the use of the gramicidin permeabilized-patch technique, which is reported to not disturb [Cl−]i, the reversal potential for spontaneous transient inward currents ( ESTICs) was −10.5 mV. This value corresponds to the peak of slow waves when they are recorded directly from ICC in situ. Inhibition of NKCC1 with bumetanide shifted ESTICs to more negative potentials within a few minutes and reduced pacemaker activity. Bumetanide had no direct effects on ANO1 or CaV3.2 channels expressed in HEK293 cells or L-type Ca2+ currents. Reducing extracellular Cl− to 10 mM shifted ESTICs to positive potentials as predicted by the Nernst equation. The relatively rapid shift in ESTICs when NKCC1 was blocked suggests that significant changes in the transmembrane Cl− gradient occur during the slow-wave cycle, possibly within microdomains formed between endoplasmic reticulum and the plasma membrane in ICC. Recovery of Cl− via NKCC1 might have additional consequences on shaping the waveforms of slow waves via Na+ entry into microdomains.

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Are interstitial cells of Cajal plurifunction cells in the gut?

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00344.2007 ◽

2008 ◽

Vol 294 (2) ◽

pp. G372-G390 ◽

Cited By ~ 40

Author(s):

Sushil K. Sarna

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Interstitial Cells Of Cajal ◽

Circular Muscle ◽

Muscle Cells ◽

Interstitial Cells ◽

Slow Waves ◽

Enteric Neurons ◽

Motility Disorders ◽

Cells Of Cajal

The proposed functions of the interstitial cells of Cajal (ICC) are to 1) pace the slow waves and regulate their propagation, 2) mediate enteric neuronal signals to smooth muscle cells, and 3) act as mechanosensors. In addition, impairments of ICC have been implicated in diverse motility disorders. This review critically examines the available evidence for these roles and offers alternate explanations. This review suggests the following: 1) The ICC may not pace the slow waves or help in their propagation. Instead, they may help in maintaining the gradient of resting membrane potential (RMP) through the thickness of the circular muscle layer, which stabilizes the slow waves and enhances their propagation. The impairment of ICC destabilizes the slow waves, resulting in attenuation of their amplitude and impaired propagation. 2) The one-way communication between the enteric neuronal varicosities and the smooth muscle cells occurs by volume transmission, rather than by wired transmission via the ICC. 3) There are fundamental limitations for the ICC to act as mechanosensors. 4) The ICC impair in numerous motility disorders. However, a cause-and-effect relationship between ICC impairment and motility dysfunction is not established. The ICC impair readily and transform to other cell types in response to alterations in their microenvironment, which have limited effects on motility function. Concurrent investigations of the alterations in slow-wave characteristics, excitation-contraction and excitation-inhibition couplings in smooth muscle cells, neurotransmitter synthesis and release in enteric neurons, and the impairment of the ICC are required to understand the etiologies of clinical motility disorders.

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Slow wave propagation and plasticity of interstitial cells of Cajal in the small intestine of diabetic rats

Experimental Physiology ◽

10.1113/expphysiol.2011.058941 ◽

2011 ◽

Vol 96 (10) ◽

pp. 1039-1048 ◽

Cited By ~ 30

Author(s):

Wim J. E. P. Lammers ◽

H. M. Al-Bloushi ◽

S. A. Al-Eisaei ◽

F. A. Al-Dhaheri ◽

B. Stephen ◽

...

Keyword(s):

Wave Propagation ◽

Small Intestine ◽

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Interstitial Cells ◽

Diabetic Rats ◽

Cells Of Cajal

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Role of gap junctions in structural arrangements of interstitial cells of Cajal and canine ileal smooth muscle

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1998.274.6.g1125 ◽

1998 ◽

Vol 274 (6) ◽

pp. G1125-G1141 ◽

Cited By ~ 12

Author(s):

Edwin E. Daniel ◽

Yu-Fang Wang ◽

Francisco S. Cayabyab

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Gap Junctions ◽

Interstitial Cells Of Cajal ◽

Circular Muscle ◽

Muscle Cells ◽

Interstitial Cells ◽

Slow Waves ◽

Circular Smooth Muscle ◽

Cells Of Cajal

We examined the structural and functional basis for pacemaking by interstitial cells of Cajal (ICC) in circular smooth muscle of the canine ileum. Gap junctions were found between ICC of myenteric plexus (MyP), occasionally between MyP ICC and outer circular smooth muscle cells, between individual outer circular smooth muscle cells, between them and ICC of the deep muscular plexus (DMP), and between DMP ICC. No visible gap junctions connected MyP ICC to longitudinal muscle cells or inner circular muscle cells. Occasionally contacts occurred between the two muscle layers. No special structures were found to connect MyP and DMP ICC networks. Octanol concentration dependently reduced the amplitude and frequency of, but did not abolish, slow waves in circular muscle in isolated ileum recorded near the MyP or the DMP. Slow waves triggered from MyP ICC by a current pulse also persisted. Contractile activity was abolished, cells were depolarized, and fast inhibitory junction potentials were reduced by octanol. We conclude that ICC pacemakers of the MyP and DMP utilize gap junctional conductances for pacemaking function but may not require them. Coupling between the two ICC networks may utilize the circular muscle syncytium.

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Excitability of canine colon circular muscle disconnected from the network of interstitial cells of Cajal

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y92-036 ◽

1992 ◽

Vol 70 (2) ◽

pp. 289-295 ◽

Cited By ~ 22

Author(s):

Louis W. C. Liu ◽

Edwin E. Daniel ◽

Jan D. Huizinga

Keyword(s):

Slow Wave ◽

Interstitial Cells Of Cajal ◽

Potassium Conductance ◽

Circular Muscle ◽

Interstitial Cells ◽

Slow Waves ◽

Oscillatory Activity ◽

Krebs Solution ◽

Ionic Mechanisms ◽

Cells Of Cajal

The 6 cpm omnipresent slow waves recorded in the circular muscle (CM) layer of canine colon are generated at the submucosal surface of the CM layer. After removal of the submucosal network of interstitial cells of Cajal (ICC), 66% of the CM preparations (25 of 38) were quiescent in Krebs solution. In the presence of carbachol, seven of nine of these spontaneously quiescent CM preparations demonstrated slow wave-like activity with mean frequency, duration and amplitude of 5.9 ± 0.4 cpm, 2.8 ± 0.5 s, and 0.8 ± 0.2 mV, respectively. Similar slow wave-like activities were induced by TEA (seven out of eight quiescent CM preparations) with frequency, duration and amplitude of 6.1 ± 0.2 cpm, 2.7 ± 0.5 s, and 1.0 ± 0.2 mV, respectively, and by BaCl2 (eight of eight quiescent CM preparations) with frequency, duration, and amplitude of 6.3 ± 0.3 cpm, 1.8 ± 0.2 s, and 0.5 ± 0.1 mV, respectively. All the induced activities were abolished in the presence of 1 μM D600. CM preparations with the submucosal ICC network intact (ICC–CM) showed slow wave activity in Krebs solution at a frequency of 6.2 ± 0.2 cpm, a duration of 3.6 ± 0.2 s, and an amplitude of 1.0 ± 0.1 mV (n = 22). When ICC–CM preparations were stimulated by BaCl2, carbachol, or TEA, the slow wave frequency did not change significantly, but the duration increased as well as the amplitude. In the presence of D600, the upstroke of slow waves remained and the frequency was not affected. The ability to generate slow wave-like activity after potassium conductance blockade in spontaneously quiescent CM disconnected from the ICC network suggested that circular muscle cells have ionic mechanisms for intrinsic oscillatory activity and are capable of actively participating in the conduction and generation of slow waves.Key words: colon, smooth muscle, interstitial cells of Cajal, canine, slow waves, excitability.

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