Spatial and temporal mapping of pacemaker activity in interstitial cells of Cajal in mouse ileum in situ

2006 ◽  
Vol 290 (5) ◽  
pp. C1411-C1427 ◽  
Author(s):  
Kyu Joo Park ◽  
Grant W. Hennig ◽  
Hyun-Tai Lee ◽  
Nick J. Spencer ◽  
Sean M. Ward ◽  
...  
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Single Cells ◽  
Normal Activity ◽  
Interstitial Cells ◽  
Slow Waves ◽  
Pacemaker Activity ◽  
Transient Wave ◽  
Wave Fronts ◽  
Inhibitory Drug ◽  
Cells Of Cajal

Spontaneous electrical pacemaker activity occurs in tunica muscularis of the gastrointestinal tract and drives phasic contractions. Interstitial cells of Cajal (ICC) are the pacemaker cells that generate and propagate electrical slow waves. We used Ca2+ imaging to visualize spontaneous rhythmicity in ICC in the myenteric region (ICC-MY) of the murine small intestine. ICC-MY, verified by colabeling with Kit antibody, displayed regular Ca2+ transients that occurred after electrical slow waves. ICC-MY formed networks, and Ca2+ transient wave fronts propagated through the ICC-MY networks at ∼2 mm/s and activated attached longitudinal muscle fibers. Nicardipine blocked Ca2+ transients in LM but had no visible effect on the transients in ICC-MY. β-Glycyrrhetinic acid reduced the coherence of propagation, causing single cells to pace independently. Thus, virtually all ICC-MYs are spontaneously active, but normal activity is organized into propagating wave fronts. Inhibitors of dihydropyridine-resistant Ca2+ entry (Ni2+ and mibefradil) and elevated external K+ reduced the coherence and velocity of propagation, eventually blocking all activity. The mitochondrial uncouplers, FCCP, and antimycin and the inositol 1,4,5-trisphosphate receptor-inhibitory drug, 2-aminoethoxydiphenyl borate, abolished rhythmic Ca2+ transients in ICC-MY. These data show that global Ca2+ transients in ICC-MYs are a reporter of electrical slow waves in gastrointestinal muscles. Imaging of ICC networks provides a unique multicellular view of pacemaker activity. The activity of ICC-MY is driven by intracellular Ca2+ handling mechanisms and entrained by voltage-dependent Ca2+ entry and coupling of cells via gap junctions.

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.

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.

scholarly journals Expression and function of a T-type Ca2+ conductance in interstitial cells of Cajal of the murine small intestine

2014 ◽  
Vol 306 (7) ◽  
pp. C705-C713 ◽  
Author(s):  
Haifeng Zheng ◽  
Kyung Sik Park ◽  
Sang Don Koh ◽  
Kenton M. Sanders
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Low Voltage ◽  
Interstitial Cells ◽  
Slow Waves ◽  
Pacemaker Activity ◽  
Inward Current ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Cells Of Cajal ◽  
Upstroke Velocity

Interstitial cells of Cajal (ICC) generate slow waves in gastrointestinal (GI) muscles. Previous studies have suggested that slow wave generation and propagation depends on a voltage-dependent Ca2+ entry mechanism with the signature of a T-type Ca2+ conductance. We studied voltage-dependent inward currents in isolated ICC. ICC displayed two phases of inward current upon depolarization: a low voltage-activated inward current and a high voltage-activated current. The latter was of smaller current density and blocked by nicardipine. Ni2+ (30 μM) or mibefradil (1 μM) blocked the low voltage-activated current. Replacement of extracellular Ca2+ with Ba2+ did not affect the current, suggesting that either charge carrier was equally permeable. Half-activation and half-inactivation occurred at −36 and −59 mV, respectively. Temperature sensitivity of the Ca2+ current was also characterized. Increasing temperature (20–30°C) augmented peak current from −7 to −19 pA and decreased the activation time from 20.6 to 7.5 ms [temperature coefficient (Q10) = 3.0]. Molecular studies showed expression of Cacna1g (Cav3.1) and Cacna1h (Cav3.2) in ICC. The temperature dependence of slow waves in intact jejunal muscles of wild-type and Cacna1h −/− mice was tested. Reducing temperature decreased the upstroke velocity significantly. Upstroke velocity was also reduced in muscles of Cacna1h −/− mice, and Ni2+ or reduced temperature had little effect on these muscles. Our data show that a T-type conductance is expressed and functional in ICC. With previous studies our data suggest that T-type current is required for entrainment of pacemaker activity within ICC and for active propagation of slow waves in ICC networks.

scholarly journals Computational modeling of anoctamin 1 calcium-activated chloride channels as pacemaker channels in interstitial cells of Cajal

2014 ◽  
Vol 306 (8) ◽  
pp. G711-G727 ◽  
Author(s):  
Rachel Lees-Green ◽  
Simon J. Gibbons ◽  
Gianrico Farrugia ◽  
James Sneyd ◽  
Leo K. Cheng
Keyword(s):  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Reversal Potential ◽  
Interstitial Cells ◽  
Slow Waves ◽  
Equilibrium Potential ◽  
Pacemaker Activity ◽  
Anoctamin 1 ◽  
Pacemaker Channel ◽  
Cells Of Cajal

Interstitial cells of Cajal (ICC) act as pacemaker cells in the gastrointestinal tract by generating electrical slow waves to regulate rhythmic smooth muscle contractions. Intrinsic Ca2+ oscillations in ICC appear to produce the slow waves by activating pacemaker currents, currently thought to be carried by the Ca2+-activated Cl− channel anoctamin 1 (Ano1). In this article we present a novel model of small intestinal ICC pacemaker activity that incorporates store-operated Ca2+ entry and a new model of Ano1 current. A series of simulations were carried out with the ICC model to investigate current controversies about the reversal potential of the Ano1 Cl− current in ICC and to predict the characteristics of the other ion channels that are necessary to generate slow waves. The model results show that Ano1 is a plausible pacemaker channel when coupled to a store-operated Ca2+ channel but suggest that small cyclical depolarizations may still occur in ICC in Ano1 knockout mice. The results predict that voltage-dependent Ca2+ current is likely to be negligible during the slow wave plateau phase. The model shows that the Cl− equilibrium potential is an important modulator of slow wave morphology, highlighting the need for a better understanding of Cl− dynamics in ICC.

scholarly journals Effects of Lubiprostone on Pacemaker Activity of Interstitial Cells of Cajal from the Mouse Colon

2014 ◽  
Vol 18 (4) ◽  
pp. 341 ◽  
Author(s):  
Han-Yi Jiao ◽  
Dong Hyun Kim ◽  
Jung Suk Ki ◽  
Kwon Ho Ryu ◽  
Seok Choi ◽  
...  
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Interstitial Cells ◽  
Pacemaker Activity ◽  
Mouse Colon ◽  
Cells Of Cajal

scholarly journals Effects of ATP on Pacemaker Activity of Interstitial Cells of Cajal from the Mouse Small Intestine

2018 ◽  
Vol 54 (1) ◽  
pp. 63
Author(s):  
Il Koo Park ◽  
Jin Ho Kim ◽  
Chan Guk Park ◽  
Man Yoo Kim ◽  
Shankar Prasad Parajuli ◽  
...  
Keyword(s):  
Small Intestine ◽  
Interstitial Cells Of Cajal ◽  
Interstitial Cells ◽  
Pacemaker Activity ◽  
Mouse Small Intestine ◽  
Cells Of Cajal

Action potential generation in the small intestine of W mutant mice that lack interstitial cells of Cajal

1996 ◽  
Vol 271 (3) ◽  
pp. G387-G399 ◽  
Author(s):  
J. Malysz ◽  
L. Thuneberg ◽  
H. B. Mikkelsen ◽  
J. D. Huizinga
Keyword(s):  
Small Intestine ◽  
Action Potentials ◽  
Interstitial Cells Of Cajal ◽  
Interstitial Cells ◽  
K Channel ◽  
Pacemaker Activity ◽  
Channel Blockade ◽  
Auerbach’S Plexus ◽  
Cells Of Cajal ◽  
Auerbach's Plexus

The small intestine of W/Wv mice lacks both the network of interstitial cells of Cajal (ICC), associated with Auerbach's plexus, and pacemaker activity, i.e., it does not generate slow-wave-type action potentials. The W/Wv muscle preparations showed a wide variety of electrical activities, ranging from total quiescence to generation of action potentials at regular or irregular frequency with or without periods of quiescence. The action potentials consisted of a slow component with superimposed spikes, preceded by a slowly developing depolarization and followed by a transient hyperpolarization. The action potentials were completely abolished by L-type Ca2+ channel blockers. W/Wv mice responded to K+ channel blockade (0.5 mM Ba2+ or 10 mM tetraethylammonium chloride) with effects on amplitude, frequency, rate of rise, and duration of the action potentials. In quiescent tissues from W/Wv mice, K+ channel blockade evoked the typical spikelike action potentials. Electron microscopy identified few methylene blue-positive cells in the W/Wv small intestine associated with Auerbach's plexus as individual ICC. Numbers of resident macrophage-like cells (MLC) and fibroblast-like cells (FLC) were significantly changed. Neither FLC nor MLC were part of a network nor did they form specialized junctions with neighboring cells as ICC do. Hence no cell type had replaced ICC at their normal morphological position associated with Auerbach's plexus. ICC were present in W/Wv mice at the deep muscular plexus in normal organization and numbers, indicating that they are not dependent on the Kit protein and do not take part in generation of pacemaker activity.

scholarly journals Molecular markers expressed in cultured and freshly isolated interstitial cells of Cajal

2000 ◽  
Vol 279 (2) ◽  
pp. C529-C539 ◽  
Author(s):  
Anne Epperson ◽  
William J. Hatton ◽  
Brid Callaghan ◽  
Philip Doherty ◽  
Rebecca L. Walker ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Small Intestine ◽  
Interstitial Cells Of Cajal ◽  
Expression Profiles ◽  
Interstitial Cells ◽  
Gastric Fundus ◽  
Soluble Form ◽  
Pacemaker Activity ◽  
Murine Small Intestine ◽  
Cells Of Cajal

Located within the tunica muscularis of the gastrointestinal (GI) tract are networks of cells known as interstitial cells of Cajal (ICC). ICC are critical for important basic functions of GI motility such as generation and propagation of slow-wave pacemaker activity and reception of regulatory inputs from the enteric nervous system. We have developed a novel procedure to identify and isolate individual ICC from freshly dispersed cell preparations of the murine small intestine and gastric fundus and to determine differential transcriptional expression We have compared the expression profiles of pacemaker ICC isolated from the murine small intestine (IC-MY) and ICC involved in neurotransmission from the gastric fundus (IC-IM). We have also compared expression profiles between ICC and smooth muscle cells (SMC) and between freshly isolated ICC and cultured ICC. Cultured ICC express smooth muscle myosin, whereas freshly dispersed ICC do not. All cell types express muscarinic receptor types M2and M3, neurokinin receptors NK1and NK3, and inhibitory receptor VIP-1, whereas only cultured ICC and SMC express VIP-2. Both cultured and freshly dispersed IC-IM and IC-MY express the soluble form of stem cell factor, whereas SMC from the gastric fundus express only the membrane-bound form.

scholarly journals Capsaicin Inhibits the Spontaneous Pacemaker Activity in Interstitial Cells of Cajal From the Small Intestine of Mouse

2010 ◽  
Vol 16 (3) ◽  
pp. 265-273 ◽  
Author(s):  
Seok Choi ◽  
Jae Myeong Sun ◽  
Pawan Kumar Shahi ◽  
Dong Chuan Zuo ◽  
Hyun Il Kim ◽  
...  
Keyword(s):  
Small Intestine ◽  
Interstitial Cells Of Cajal ◽  
Interstitial Cells ◽  
Pacemaker Activity ◽  
Cells Of Cajal

scholarly journals Intracellular Ca2+ release from endoplasmic reticulum regulates slow wave currents and pacemaker activity of interstitial cells of Cajal

2015 ◽  
Vol 308 (8) ◽  
pp. C608-C620 ◽  
Author(s):  
Mei Hong Zhu ◽  
Tae Sik Sung ◽  
Kate O'Driscoll ◽  
Sang Don Koh ◽  
Kenton M. Sanders
Keyword(s):  
Slow Wave ◽  
Interstitial Cells Of Cajal ◽  
Ryanodine Receptors ◽  
Interstitial Cells ◽  
Pacemaker Activity ◽  
Current Clamp ◽  
Anoctamin 1 ◽  
Intracellular Ca ◽  
Inward Currents ◽  
Cells Of Cajal

Interstitial cells of Cajal (ICC) provide pacemaker activity in gastrointestinal muscles that underlies segmental and peristaltic contractions. ICC generate electrical slow waves that are due to large-amplitude inward currents resulting from anoctamin 1 (ANO1) channels, which are Ca2+-activated Cl− channels. We investigated the hypothesis that the Ca2+ responsible for the stochastic activation of ANO1 channels during spontaneous transient inward currents (STICs) and synchronized activation of ANO1 channels during slow wave currents comes from intracellular Ca2+ stores. ICC, obtained from the small intestine of Kit +/copGFP mice, were studied under voltage and current clamp to determine the effects of blocking Ca2+ uptake into stores and release of Ca2+ via inositol 1,4,5-trisphosphate (IP3)-dependent and ryanodine-sensitive channels. Cyclocpiazonic acid, thapsigargin, 2-APB, and xestospongin C inhibited STICs and slow wave currents. Ryanodine and tetracaine also inhibited STICs and slow wave currents. Store-active compounds had no direct effects on ANO1 channels expressed in human embryonic kidney-293 cells. Under current clamp, store-active drugs caused significant depolarization of ICC and reduced spontaneous transient depolarizations (STDs). After block of ryanodine receptors with ryanodine and tetracaine, repolarization did not restore STDs. ANO1 expressed in ICC has limited access to cytoplasmic Ca2+ concentration, suggesting that pacemaker activity depends on Ca2+ dynamics in restricted microdomains. Our data from studies of isolated ICC differ somewhat from studies on intact muscles and suggest that release of Ca2+ from both IP3 and ryanodine receptors is important in generating pacemaker activity in ICC.

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