Pacemaker potentials generated by interstitial cells of Cajal in the murine intestine

2005 ◽  
Vol 288 (3) ◽  
pp. C710-C720 ◽  
Author(s):  
Yoshihiko Kito ◽  
Sean M. Ward ◽  
Kenton M. Sanders
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Interstitial Cells ◽  
Slow Waves ◽  
Pacemaker Activity ◽  
Dependent Manner ◽  
Plateau Potential ◽  
Pacemaker Potentials ◽  
Cells Of Cajal

Pacemaker potentials were recorded in situ from myenteric interstitial cells of Cajal (ICC-MY) in the murine small intestine. The nature of the two components of pacemaker potentials (upstroke and plateau) were investigated and compared with slow waves recorded from circular muscle cells. Pacemaker potentials and slow waves were not blocked by nifedipine (3 μM). In the presence of nifedipine, mibefradil, a voltage-dependent Ca2+ channel blocker, reduced the amplitude, frequency, and rate of rise of upstroke depolarization (d V/d tmax) of pacemaker potentials and slow waves in a dose-dependent manner (1–30 μM). Mibefradil (30 μM) changed the pattern of pacemaker potentials from rapidly rising, high-frequency events to slowly depolarizing, low-frequency events with considerable membrane noise (unitary potentials) between pacemaker potentials. Caffeine (3 mM) abolished pacemaker potentials in the presence of mibefradil. Pinacidil (10 μM), an ATP-sensitive K+ channel opener, hyperpolarized ICC-MY and increased the amplitude and d V/d tmax without affecting frequency. Pinacidil hyperpolarized smooth muscle cells and attenuated the amplitude and d V/d tmax of slow waves without affecting frequency. The effects of pinacidil were blocked by glibenclamide (10 μM). These data suggest that slow waves are electrotonic potentials driven by pacemaker potentials. The upstroke component of pacemaker potentials is due to activation of dihydropyridine-resistant Ca2+ channels, and this depolarization entrains pacemaker activity to create the plateau potential. The plateau potential may be due to summation of unitary potentials generated by individual or small groups of pacemaker units in ICC-MY. Entrainment of unitary potentials appears to depend on Ca2+ entry during upstroke depolarization.

Are interstitial cells of Cajal plurifunction cells in the gut?

2008 ◽  
Vol 294 (2) ◽  
pp. G372-G390 ◽  
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.

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

1998 ◽  
Vol 274 (6) ◽  
pp. G1125-G1141 ◽  
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.

Canine colonic circular muscle generates action potentials without the pacemaker component

1994 ◽  
Vol 72 (1) ◽  
pp. 70-81 ◽  
Author(s):  
Louis W. C. Liu ◽  
Jan D. Huizinga
Keyword(s):  
Smooth Muscle ◽  
Calcium Channel ◽  
Action Potentials ◽  
Interstitial Cells Of Cajal ◽  
Longitudinal Muscle ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Interstitial Cells ◽  
Slow Waves ◽  
Cells Of Cajal

Two dominant types of action potentials in canine colon are slow wave type action potentials (slow waves) and spike-like action potentials (SLAPs). The slow waves, originating at the submuscular surface where a network of interstitial cells of Cajal (ICCs) is found, possess a pacemaker component. Activation of the pacemaker component is insensitive to voltage changes and L-type calcium channel blockers, and is postulated to involve a metabolic clock sensitive to cyclic AMP. SLAPs are more prominent in the longitudinal muscle. To understand the contribution circular muscle cells make to the generation of these action potentials, a circular muscle preparation (devoid of the submuscular ICC – smooth muscle network, longitudinal muscle, and myenteric plexus) was developed. Circular muscle preparations were spontaneously quiescent, with a resting membrane potential of −62.9 ± 0.6 mV. Ba2+ (0.5 mM) depolarized the cells to −51.8 ± 0.6 mV and induced electrical oscillations with a frequency, duration, amplitude, and rate of rise equal to 6.6 ± 0.4 cpm, 2.2 ± 0.2 s, 19.4 ± 0.9 mV, and 21.8 ± 1.7 mV/s, respectively. In most cases, Ba2+-induced oscillations were preceded by a prepotential of 4.4 ± 0.3 mV, with a rate of rise of 1.1 ± 0.1 mV/s. Ba2+-induced oscillations were abolished by 1 μM D600 as well as by repolarization of 6–12 mV. Addition of 0.1 μM Bay K8644 in the presence of Ba2+ further depolarized circular muscle cells to −42.4 ± 0.8 mV and increased the oscillation frequency to 16.8 ± 1.8 cpm. The electrical oscillations induced in circular muscle preparations by Ba2+ and Bay K8644 were similar to the SLAPs exhibited by the isolated longitudinal muscle layer, indicating that generation of SLAPs is an intrinsic property of smooth muscle cells. Forskolin (1 μM), previously shown to dramatically decrease the frequency but not the amplitude of slow waves in preparations including the submuscular ICC network, decreased the amplitude of the Ba2+-induced oscillations in circular muscle preparations without changing the frequency. These results provide strong evidence for the hypothesis that the submuscular ICC – smooth muscle network is essential for the initiation of the pacemaker component of the colonic slow waves. The mechanism for regulating the frequency of slow waves is different from that responsible for the Ba2+-induced oscillations in circular muscle preparations. Circular muscle cells are shown to be excitable and capable of generating oscillatory activity dominated by L-type calcium channel activity, which is regulated by K+ conductance.Key words: interstitial cells of Cajal, smooth muscle, dog colon, barium chloride, potassium conductance, Bay K8644, pacemaking activity.

Neuromuscular structures in opossum esophagus: role of interstitial cells of Cajal

1984 ◽  
Vol 246 (3) ◽  
pp. G305-G315 ◽  
Author(s):  
E. E. Daniel ◽  
V. Posey-Daniel
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Interstitial Cells Of Cajal ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Interstitial Cells ◽  
Complete Relaxation ◽  
Granular Vesicles ◽  
Cells Of Cajal

The structures of the lower esophageal sphincter (LES) and body circular muscle (BCM) from opossum were compared as to neural and muscular structures and the structural relations of interstitial cells of Cajal to nerves and muscle cells. Both LES and BCM were densely innervated by nerves with varicosities containing many small agranular vesicles and a few large granular vesicles. These nerves were more closely related structurally to the interstitial cells of Cajal than to smooth muscle cells. More gap junctions were observed between smooth muscle cells and between interstitial cells of Cajal and smooth muscle cells in BCM than in LES. Those between smooth muscle cells were larger in BCM. Complete relaxation of the LES strip by isoproterenol reduced these differences but did not eliminate them. The finding that interstitial cells of Cajal often had gap-junction contacts to smooth muscle and close associations with nerves is consistent with the hypothesis that interstitial cells are intercalated between the nerves and muscles and may mediate nerve responses. These findings also suggest that LES muscle cells may be less well coupled electrically than BCM muscle cells.

scholarly journals Menthol Modulates Pacemaker Potentials through TRPA1 Channels in Cultured Interstitial Cells of Cajal from Murine Small Intestine

2016 ◽  
Vol 38 (5) ◽  
pp. 1869-1882 ◽  
Author(s):  
Hyun Jung Kim ◽  
Jinhong Wie ◽  
Insuk So ◽  
Myeong Ho Jung ◽  
Ki-Tae Ha ◽  
...  
Keyword(s):  
Small Intestine ◽  
Membrane Potential ◽  
Interstitial Cells Of Cajal ◽  
Rho Kinase ◽  
Thromboxane A2 ◽  
Interstitial Cells ◽  
Dependent Manner ◽  
Induced Membrane ◽  
Pacemaker Potentials ◽  
Cells Of Cajal

Background/Aims: ICCs are the pacemaker cells responsible for slow waves in gastrointestinal (GI) smooth muscle, and generate periodic pacemaker potentials in current-clamp mode. Methods: The effects of menthol on the pacemaker potentials of cultured interstitial cells of Cajal (ICCs) from mouse small intestine were studied using the whole cell patch clamp technique. Results: Menthol (1 - 10 μM) was found to induce membrane potential depolarization in a concentration-dependent manner. The effects of various TRP channel antagonists were examined to investigate the receptors involved. The addition of the TRPM8 antagonist, AMTB, did not block menthol-induced membrane potential depolarizations, but TRPA1 antagonists (A967079 or HC-030031) blocked the effects of menthol, as did intracellular GDPβS. Furthermore, external and internal Ca2+ levels were found to depolarize menthol-induced membrane potentials, whereas external Na+ was not. Y-27632 (a Rho kinase inhibitor), SC-560 (a selective COX 1 inhibitor), NS-398 (a selective COX 2 inhibitor), ozagrel (a thromboxane A2 synthase inhibitor) and SQ-29548 (highly selective thromboxane receptor antagonist) were used to investigate the involvements of Rho-kinase, cyclooxygenase (COX), and the thromboxane pathway in menthol-induced membrane potential depolarizations, and all inhibitors were found to block the effect of menthol. Conclusions: These results suggest that menthol-induced membrane potential depolarizations occur in a G-protein-, Ca2+-, Rho-kinase-, COX-, and thromboxane A2-dependent manner via TRPA1 receptor in cultured ICCs in murine small intestine. The study shows ICCs are targeted by menthol and that this interaction can affect intestinal motility.

Selective accumulation of methylene blue by interstitial cells of Cajal in canine colon

1993 ◽  
Vol 264 (1) ◽  
pp. G64-G73 ◽  
Author(s):  
L. W. Liu ◽  
L. Thuneberg ◽  
E. E. Daniel ◽  
J. D. Huizinga
Keyword(s):  
Methylene Blue ◽  
Interstitial Cells Of Cajal ◽  
Three Dimensional ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Muscle Layer ◽  
Interstitial Cells ◽  
Resting Membrane Potential ◽  
Selective Staining ◽  
Cells Of Cajal

The network of interstitial cells of Cajal (ICC) at the submucosal surface of the canine colon was selectively stained by incubation with 15-50 microM methylene blue for 30-45 min. The network was composed of regularly scattered ICC cell bodies interconnected by long processes. Circular muscle cells were unstained. Staining of neurons was limited to one or two axons within bundles. The ICC network had a thickness of a single cell, since no overlapping of ICC cell bodies was observed. The ICC network connected the circular muscle cells at the submucosal surface across the septa which circumferentially divided the circular muscle into lamellae. Methylene blue at 50 microM slightly decreased the resting membrane potential and increased the duration of slow waves, leading to an increase in the force of phasic contractions, with no significant influence on other slow-wave parameters. Methylene blue produced neither electrophysiological nor mechanical effects on circular muscle preparations from which the submuscular ICC network was removed, indicating that the excitatory effects of methylene blue on the full-thickness circular muscle layer were mediated by ICC. In summary, the three-dimensional aspects of the submuscular ICC network can be visualized after selective staining by methylene blue. This staining does not affect physiological characteristics of smooth muscle cells.

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

2016 ◽  
Vol 311 (6) ◽  
pp. G1037-G1046 ◽  
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.

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.

scholarly journals Caffeine inhibits nonselective cationic currents in interstitial cells of Cajal from the murine jejunum

2009 ◽  
Vol 297 (4) ◽  
pp. C971-C978 ◽  
Author(s):  
Nan Ge Jin ◽  
Sang Don Koh ◽  
Kenton M. Sanders
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Interstitial Cells ◽  
Equilibrium Potential ◽  
Cation Channels ◽  
Pacemaker Activity ◽  
Dependent Manner ◽  
Current Clamp ◽  
Concentration Dependent Manner ◽  
Nonselective Cation Channels ◽  
Cells Of Cajal

Interstitial cells of Cajal (ICC) discharge unitary potentials in gastrointestinal muscles that constitute the basis for pacemaker activity. Caffeine has been used to block unitary potentials, but the ionic conductance responsible for unitary potentials is controversial. We investigated currents in cultured ICC from murine jejunum that may underlie unitary potentials and studied the effects of caffeine. Networks of ICC generated slow wave events under current clamp, and these events were blocked by caffeine in a concentration-dependent manner. Single ICC generated spontaneous transient inward currents (STICs) under voltage clamp at −60 mV and noisy voltage fluctuations in current clamp. STICs were unaffected when the equilibrium potential for Cl− ( ECl) was set to −60 mV (excluding Cl− currents) and reversed at 0 mV, demonstrating that a nonselective cationic conductance, and not a Cl− conductance, is responsible for STICs in ICC. Caffeine inhibited STICs in a concentration-dependent manner. Reduced intracellular Ca2+ and calmidazolium (CMZ; 1 μM) activated persistent inward, nonselective cation currents in ICC. Currents activated by CMZ and by dialysis of cells with 10 mM BAPTA were also inhibited by caffeine. Excised inside-out patches contained channels that exhibited spontaneous openings, and resulting currents reversed at 0 mV. Channel openings were increased by reducing Ca2+ concentration from 10−6 M to 10−8 M. CMZ (1 μM) also increased openings of nonselective cation channels. Spontaneous currents and channels activated by CMZ were inhibited by caffeine (5 mM). The findings demonstrate that the Ca2+-inhibited nonselective cation channels that generate STICs in ICC are blocked directly by caffeine. STICs are responsible for unitary potentials in intact muscles, and the block of these events by caffeine is consistent with the idea that a nonselective cation conductance underlies unitary potentials in ICC.

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