51
|
McCann CJ, Hwang SJ, Hennig GW, Ward SM, Sanders KM. Bone Marrow Derived Kit-positive Cells Colonize the Gut but Fail to Restore Pacemaker Function in Intestines Lacking Interstitial Cells of Cajal. J Neurogastroenterol Motil 2014; 20:326-37. [PMID: 24847840 PMCID: PMC4102151 DOI: 10.5056/jnm14026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/01/2014] [Accepted: 04/09/2014] [Indexed: 12/28/2022] Open
Abstract
Background/Aims Several motility disorders are associated with disruption of interstitial cells of Cajal (ICC), which provide important functions, such as pacemaker activity, mediation of neural inputs and responses to stretch in the gastrointestinal (GI) tract. Restoration of ICC networks may be therapeutic for GI motor disorders. Recent reports have suggested that Kit+ cells can be restored to the GI tract via bone marrow (BM) transplantation. We tested whether BM derived cells can lead to generation of functional activity in intestines naturally lacking ICC. Methods BM cells from Kit+/copGFP mice, in which ICC are labeled with a green fluorescent protein, were transplanted into W/WV intestines, lacking ICC. After 12 weeks the presence of ICC was analyzed by immunohistochemistry and functional analysis of electrical behavior and contractile properties. Results After 12 weeks copGFP+ BM derived cells were found within the myenteric region of intestines from W/WV mice, typically populated by ICC. Kit+ cells failed to develop interconnections typical of ICC in the myenteric plexus. The presence of Kit+ cells was verified with Western analysis. BM cells failed to populate the region of the deep muscular plexus where normal ICC density, associated with the deep muscular plexus, is found in W/WV mice. Engraftment of Kit+-BM cells resulted in the development of unitary potentials in transplanted muscles, but slow wave activity failed to develop. Motility analysis showed that intestinal movements in transplanted animals were abnormal and similar to untransplanted W/WV intestines. Conclusions BM derived Kit+ cells colonized the gut after BM transplantation, however these cells failed to develop the morphology and function of mature ICC.
Collapse
Affiliation(s)
- Conor J McCann
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; University College London Institute of Child Health, Birth Defects Research Center, Neural Development Unit, London, UK
| | - Sung-Jin Hwang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| |
Collapse
|
52
|
Hart KA, Sherlock CE, Davern AJ, Lewis TH, Robertson TP. Effect of N
-butylscopolammonium bromide on equine ileal smooth muscle activity in an ex vivo
model. Equine Vet J 2014; 47:450-5. [DOI: 10.1111/evj.12293] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 04/12/2014] [Indexed: 11/30/2022]
Affiliation(s)
- K. A. Hart
- Department of Large Animal Medicine; University of Georgia College of Veterinary Medicine; Athens USA
| | - C. E. Sherlock
- Department of Large Animal Medicine; University of Georgia College of Veterinary Medicine; Athens USA
| | - A. J. Davern
- Department of Large Animal Medicine; University of Georgia College of Veterinary Medicine; Athens USA
| | - T. H. Lewis
- Department of Large Animal Medicine; University of Georgia College of Veterinary Medicine; Athens USA
| | - T. P. Robertson
- Department of Large Animal Medicine; University of Georgia College of Veterinary Medicine; Athens USA
| |
Collapse
|
53
|
Zheng H, Park KS, Koh SD, Sanders KM. Expression and function of a T-type Ca2+ conductance in interstitial cells of Cajal of the murine small intestine. Am J Physiol Cell Physiol 2014; 306:C705-13. [PMID: 24477235 DOI: 10.1152/ajpcell.00390.2013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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 Ca(2+) entry mechanism with the signature of a T-type Ca(2+) 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. Ni(2+) (30 μM) or mibefradil (1 μM) blocked the low voltage-activated current. Replacement of extracellular Ca(2+) with Ba(2+) 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 Ca(2+) 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 Ni(2+) 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.
Collapse
Affiliation(s)
- Haifeng Zheng
- Department of Physiology and Cell Biology, University of Nevada, School of Medicine, Reno, Nevada; and
| | | | | | | |
Collapse
|
54
|
Sathar S, Trew ML, Du P, O'Grady G, Cheng LK. A biophysically based finite-state machine model for analyzing gastric experimental entrainment and pacing recordings. Ann Biomed Eng 2013; 42:858-70. [PMID: 24276722 DOI: 10.1007/s10439-013-0949-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 11/19/2013] [Indexed: 12/14/2022]
Abstract
Gastrointestinal motility is coordinated by slow waves (SWs) generated by the interstitial cells of Cajal (ICC). Experimental studies have shown that SWs spontaneously activate at different intrinsic frequencies in isolated tissue, whereas in intact tissues they are entrained to a single frequency. Gastric pacing has been used in an attempt to improve motility in disorders such as gastroparesis by modulating entrainment, but the optimal methods of pacing are currently unknown. Computational models can aid in the interpretation of complex in vivo recordings and help to determine optimal pacing strategies. However, previous computational models of SW entrainment are limited to the intrinsic pacing frequency as the primary determinant of the conduction velocity, and are not able to accurately represent the effects of external stimuli and electrical anisotropies. In this paper, we present a novel computationally efficient method for modeling SW propagation through the ICC network while accounting for conductivity parameters and fiber orientations. The method successfully reproduced experimental recordings of entrainment following gastric transection and the effects of gastric pacing on SW activity. It provides a reliable new tool for investigating gastric electrophysiology in normal and diseased states, and to guide and focus future experimental studies.
Collapse
Affiliation(s)
- Shameer Sathar
- Auckland Bioengineering Institute, University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | | | | | | | | |
Collapse
|
55
|
Hurtado R, Bub G, Herzlinger D. A molecular signature of tissues with pacemaker activity in the heart and upper urinary tract involves coexpressed hyperpolarization-activated cation and T-type Ca2+ channels. FASEB J 2013; 28:730-9. [PMID: 24189942 DOI: 10.1096/fj.13-237289] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Renal pacemakers set the origin and frequency of the smooth muscle contractions that propel wastes from the kidney to the bladder. Although congenital defects impairing this peristalsis are a leading cause of pediatric renal failure, the mechanisms underlying renal pacemaker activity remain unknown. Using ratiometric optical mapping and video microscopy, we discovered that hyperpolarization-activated cation (HCN) channel block with the specific anatagonist ZD7288 (30 μm; IC50) abolished the pacemaker depolarizations that initiate murine upper urinary tract peristalsis. Optical mapping and immunohistochemistry indicate that pacemaker potentials are generated by cells expressing HCN isoform-3, and that HCN3(+) cells are coupled to definitive smooth muscle via gap junctions. Furthermore, we demonstrate that HCN3(+) cells coexpress T-type Ca(2+) (TTC) channels and that TTC channel inhibition with R(-)efonidipine or NNC55-0396 decreased contractile frequency in a dose-dependent manner. Collectively, these data demonstrate that HCN3(+)/TTC(+) cells are the pacemakers that set the origin and rate of upper urinary tract peristalsis. These results reveal a conserved mechanism controlling autorhythmicity in 2 distinct muscle types, as HCN and TTC channels also mediate cardiac pacemaker activity. Moreover, these findings have translational applications, including the development of novel diagnostics to detect fetal urinary tract motility defects prior to renal damage.-Hurtado, R., Bub, G., Herzlinger, D. A molecular signature of tissues with pacemaker activity in the heart and upper urinary tract involves coexpressed hyperpolarization-activated cation and T-type Ca(2+) channels.
Collapse
Affiliation(s)
- Romulo Hurtado
- 1Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY 10021, USA.
| | | | | |
Collapse
|
56
|
Taniguchi M, Kajioka S, Shozib HB, Sawamura K, Nakayama S. Spatial analysis of slowly oscillating electric activity in the gut of mice using low impedance arrayed microelectrodes. PLoS One 2013; 8:e75235. [PMID: 24124480 PMCID: PMC3790767 DOI: 10.1371/journal.pone.0075235] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 08/13/2013] [Indexed: 01/25/2023] Open
Abstract
Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm2. The size of each recording electrode was 50×50 µm2, however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/Wv mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/Wv mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.
Collapse
Affiliation(s)
- Mizuki Taniguchi
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shunichi Kajioka
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Habibul B. Shozib
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Kenta Sawamura
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shinsuke Nakayama
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
- * E-mail:
| |
Collapse
|
57
|
Angeli TR, Du P, Paskaranandavadivel N, Janssen PWM, Beyder A, Lentle RG, Bissett IP, Cheng LK, O'Grady G. The bioelectrical basis and validity of gastrointestinal extracellular slow wave recordings. J Physiol 2013; 591:4567-79. [PMID: 23713030 PMCID: PMC3784199 DOI: 10.1113/jphysiol.2013.254292] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 05/23/2013] [Indexed: 12/27/2022] Open
Abstract
Gastrointestinal extracellular recordings have been a core technique in motility research for a century. However, the bioelectrical basis of extracellular data has recently been challenged by claims that these techniques preferentially assay movement artifacts, cannot reproduce the underlying slow wave kinetics, and misrepresent the true slow wave frequency. These claims motivated this joint experimental-theoretical study, which aimed to define the sources and validity of extracellular potentials. In vivo extracellular recordings and video capture were performed in the porcine jejunum, before and after intra-arterial nifedipine administration. Gastric extracellular recordings were recorded simultaneously using conventional serosal contact and suction electrodes, and biphasic and monophasic extracellular potentials were simulated in a biophysical model. Contractions were abolished by nifedipine, but extracellular slow waves persisted, with unchanged amplitude, downstroke rate, velocity, and downstroke width (P>0.10 for all), at reduced frequency (24% lower; P=0.03). Simultaneous suction and conventional serosal extracellular recordings were identical in phase (frequency and activation-recovery interval), but varied in morphology (monophasic vs. biphasic; downstroke rate and amplitude: P<0.0001). Simulations demonstrated the field contribution of current flow to extracellular potential and quantified the effects of localised depolarisation due to suction pressure on extracellular potential morphology. In sum, these results demonstrate that gastrointestinal extracellular slow wave recordings cannot be explained by motion artifacts, and are of a bioelectrical origin that is highly consistent with the underlying biophysics of slow wave propagation. Motion suppression is shown to be unnecessary as a routine control in in vivo extracellular studies, supporting the validity of the extant gastrointestinal extracellular literature.
Collapse
Affiliation(s)
- Timothy R Angeli
- G. O'Grady: Auckland Bioengineering Institute, Private Bag 92019, Auckland 1142, New Zealand.
| | | | | | | | | | | | | | | | | |
Collapse
|
58
|
Si X, Huang L, Gong Y, Lu J, Lin L. Role of calcium in activation of hyperpolarization-activated cyclic nucleotide-gated channels caused by cholecystokinin octapeptide in interstitial cells of cajal. Digestion 2012; 85:266-75. [PMID: 22538231 DOI: 10.1159/000337077] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 02/07/2012] [Indexed: 02/04/2023]
Abstract
BACKGROUND Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate pacemaker activity in some cardiac cells and neurons. Little is known about the effects of cholecystokinin octapeptide (CCK-8) on HCN channels and excitability of murine interstitial cells of Cajal (ICCs). METHODS In the present study, the effects and mechanisms of CCK-8 on HCN channels were investigated by measuring mechanical contraction of smooth muscle strips and ionic channels of ICCs in murine gastric antrum. RESULTS Sulfated CCK-8 (CCK-8S) was used, and we found that CCK-8S increased the contraction of smooth muscle strips in the gastric antrum, which could be suppressed by specific HCN channel blockers CsCl and ZD7288. Extracellular calcium could also intensify the contraction. Under the same conditions, when antral strips were exposed to calcium ion (Ca²⁺)-free solution, no significant changes could be recorded with CCK-8S or ZD7288. Isolated ICCs from the murine gastric antrum identified by specific c-Kit antibody primers were chosen for electrophysiological recordings. HCN current (I(h)) of cultured ICCs was studied by whole-cell patch clamp techniques. A spontaneous transient inward current was recorded in ICCs, which could be inhibited by addition of CsCl and ZD7288; the current proved to be I(h). CCK-8S-facilitated I(h) in cultured ICCs could be inhibited by CsCl and ZD7288. When cultured ICCs were exposed to Ca²⁺-free solution, no significant changes could be recorded by application of CCK-8S on I(h), which proved extracellular calcium might have an excitatory effect on HCN channels. CONCLUSION We demonstrate that HCN channels are present in ICCs in the murine gastric antrum; they might be an important regulator of ICC excitability and pacemaker activity and are strongly affected by CCK-8S. Extracellular calcium might be a trigger in the activation of HCN channels caused by CCK-8S in cultured ICCs.
Collapse
Affiliation(s)
- Xinmin Si
- Department of Gastroenterology, The First Affiliated Hospital of Nanjing Medical University, Guangzhou Road 300, Nanjing 210029, China.
| | | | | | | | | |
Collapse
|
59
|
Sanders KM, Koh SD, Ro S, Ward SM. Regulation of gastrointestinal motility--insights from smooth muscle biology. Nat Rev Gastroenterol Hepatol 2012; 9:633-45. [PMID: 22965426 PMCID: PMC4793911 DOI: 10.1038/nrgastro.2012.168] [Citation(s) in RCA: 270] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Gastrointestinal motility results from coordinated contractions of the tunica muscularis, the muscular layers of the alimentary canal. Throughout most of the gastrointestinal tract, smooth muscles are organized into two layers of circularly or longitudinally oriented muscle bundles. Smooth muscle cells form electrical and mechanical junctions between cells that facilitate coordination of contractions. Excitation-contraction coupling occurs by Ca(2+) entry via ion channels in the plasma membrane, leading to a rise in intracellular Ca(2+). Ca(2+) binding to calmodulin activates myosin light chain kinase; subsequent phosphorylation of myosin initiates cross-bridge cycling. Myosin phosphatase dephosphorylates myosin to relax muscles, and a process known as Ca(2+) sensitization regulates the activity of the phosphatase. Gastrointestinal smooth muscles are 'autonomous' and generate spontaneous electrical activity (slow waves) that does not depend upon input from nerves. Intrinsic pacemaker activity comes from interstitial cells of Cajal, which are electrically coupled to smooth muscle cells. Patterns of contractile activity in gastrointestinal muscles are determined by inputs from enteric motor neurons that innervate smooth muscle cells and interstitial cells. Here we provide an overview of the cells and mechanisms that generate smooth muscle contractile behaviour and gastrointestinal motility.
Collapse
|
60
|
Doyle C, Sergeant GP, Hollywood MA, McHale NG, Thornbury KD. Effects of Phenylephrine on Spontaneous Activity and L‐Type Ca2+ Current in Isolated Corpus Cavernosum Myocytes. J Sex Med 2012; 9:2795-805. [DOI: 10.1111/j.1743-6109.2012.02847.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
61
|
Blair PJ, Bayguinov Y, Sanders KM, Ward SM. Interstitial cells in the primate gastrointestinal tract. Cell Tissue Res 2012; 350:199-213. [PMID: 22864981 DOI: 10.1007/s00441-012-1468-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 06/20/2012] [Indexed: 02/06/2023]
Abstract
Kit immunohistochemistry and confocal reconstructions have provided detailed 3-dimensional images of ICC networks throughout the gastrointestinal (GI) tract. Morphological criteria have been used to establish that different classes of ICC exist within the GI tract and physiological studies have shown that these classes have distinct physiological roles in GI motility. Structural studies have focused predominately on rodent models and less information is available on whether similar classes of ICC exist within the GI tracts of humans or non-human primates. Using Kit immunohistochemistry and confocal imaging, we examined the 3-dimensional structure of ICC throughout the GI tract of cynomolgus monkeys. Whole or flat mounts and cryostat sections were used to examine ICC networks in the lower esophageal sphincter (LES), stomach, small intestine and colon. Anti-histamine antibodies were used to distinguish ICC from mast cells in the lamina propria. Kit labeling identified complex networks of ICC populations throughout the non-human primate GI tract that have structural characteristics similar to that described for ICC populations in rodent models. ICC-MY formed anastomosing networks in the myenteric plexus region. ICC-IM were interposed between smooth muscle cells in the stomach and colon and were concentrated within the deep muscular plexus (ICC-DMP) of the intestine. ICC-SEP were found in septal regions of the antrum that separated circular muscle bundles. Spindle-shaped histamine(+) mast cells were found in the lamina propria throughout the GI tract. Since similar sub-populations of ICC exist within the GI tract of primates and rodents and the use of rodents to study the functional roles of different classes of ICC is warranted.
Collapse
Affiliation(s)
- Peter J Blair
- Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | | | | | | |
Collapse
|
62
|
Abstract
The fluorescent dye Lucifer yellow (LY) was introduced in 1978, and has been extremely useful in studying cell structure and communications. This dye has been used mostly for labelling cells by intracellular injection from microelectrodes. This review describes the numerous applications of LY, with emphasis on the enteric nervous system and interstitial cells of Cajal. Of particular importance is the dye coupling method, which enables the detection of cell coupling by gap junctions.
Collapse
Affiliation(s)
- Menachem Hanani
- Laboratory of Experimental Surgery, Hadassah-Hebrew University Medical Center, Mount Scopus, Jerusalem, Israel.
| |
Collapse
|
63
|
Beyder A, Farrugia G. Targeting ion channels for the treatment of gastrointestinal motility disorders. Therap Adv Gastroenterol 2012; 5:5-21. [PMID: 22282704 PMCID: PMC3263980 DOI: 10.1177/1756283x11415892] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Gastrointestinal (GI) functional and motility disorders are highly prevalent and responsible for long-term morbidity and sometimes mortality in the affected patients. It is estimated that one in three persons has a GI functional or motility disorder. However, diagnosis and treatment of these widespread conditions remains challenging. This partly stems from the multisystem pathophysiology, including processing abnormalities in the central and peripheral (enteric) nervous systems and motor dysfunction in the GI wall. Interstitial cells of Cajal (ICCs) are central to the generation and propagation of the cyclical electrical activity and smooth muscle cells (SMCs) are responsible for electromechanical coupling. In these and other excitable cells voltage-sensitive ion channels (VSICs) are the main molecular units that generate and regulate electrical activity. Thus, VSICs are potential targets for intervention in GI motility disorders. Research in this area has flourished with advances in the experimental methods in molecular and structural biology and electrophysiology. However, our understanding of the molecular mechanisms responsible for the complex and variable electrical behavior of ICCs and SMCs remains incomplete. In this review, we focus on the slow waves and action potentials in ICCs and SMCs. We describe the constituent VSICs, which include voltage-gated sodium (Na(V)), calcium (Ca(V)), potassium (K(V), K(Ca)), chloride (Cl(-)) and nonselective ion channels (transient receptor potentials [TRPs]). VSICs have significant structural homology and common functional mechanisms. We outline the approaches and limitations and provide examples of targeting VSICs at the pores, voltage sensors and alternatively spliced sites. Rational drug design can come from an integrated view of the structure and mechanisms of gating and activation by voltage or mechanical stress.
Collapse
Affiliation(s)
- Arthur Beyder
- Enteric Neuroscience Program, Division of Gastroenterology and Hepatology, Department of Medicine, Mayo Clinic, Rochester, MN, USA
| | | |
Collapse
|
64
|
Rhee PL, Lee JY, Son HJ, Kim JJ, Rhee JC, Kim S, Koh SD, Hwang SJ, Sanders KM, Ward SM. Analysis of pacemaker activity in the human stomach. J Physiol 2011; 589:6105-18. [PMID: 22005683 DOI: 10.1113/jphysiol.2011.217497] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Extracellular electrical recording and studies using animal models have helped establish important concepts of human gastric physiology. Accepted standards include electrical quiescence in the fundus, 3 cycles per minute (cpm) pacemaker activity in corpus and antrum, and a proximal-to-distal slow wave frequency gradient. We investigated slow wave pacemaker activity, contractions and distribution of interstitial cells of Cajal (ICC) in human gastric muscles. Muscles were obtained from patients undergoing gastric resection for cancer, and the anatomical locations of each specimen were mapped by the operating surgeon to 16 standardized regions of the stomach. Electrical slow waves were recorded with intracellular microelectrodes and contractions were recorded by isometric force techniques. Slow waves were routinely recorded from gastric fundus muscles. These events had similar waveforms as slow waves in more distal regions and were coupled to phasic contractions. Gastric slow wave frequency was significantly greater than 3 cpm in all regions of the stomach. Antral slow wave frequency often exceeded the highest frequency of pacemaker activity in the corpus. Chronotropic mechanisms such as muscarinic and prostaglandin receptor binding, stretch, extracelluar Ca(2+) and temperature were unable to explain the observed slow wave frequency that exceeded accepted normal levels. Muscles from all regions through the thickness of the muscularis demonstrated intrinsic pacemaker activity, and this corresponded with the widespread distribution in ICC we mapped throughout the tunica muscularis. Our findings suggest that extracellular electrical recording has underestimated human slow wave frequency and mechanisms of human gastric function may differ from standard laboratory animal models.
Collapse
Affiliation(s)
- Poong-Lyul Rhee
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
65
|
Shigemasa Y, Kito Y, Hashitani H, Suzuki H. Factors which determine the duration of follower potentials in longitudinal smooth muscle isolated from the guinea-pig stomach antrum. J Smooth Muscle Res 2011; 47:89-110. [PMID: 21979408 DOI: 10.1540/jsmr.47.89] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In isolated longitudinal muscle tissues of the guinea-pig stomach antrum, recording electrical responses from smooth muscle cells revealed a periodical generation of follower potentials with variable durations. The I-D relationship, made by plotting the duration as a function of the interval before generating follower potential, was linear. Experiments were carried out to investigate the effects of chemicals which had been known to modulate the release of Ca(2+) from the internal stores (2-aminoethoxy-diphenyl-borate, cyclopiazonic acid, caffeine), inhibit mitochondrial metabolic activity (m-chlorophenyl hydrazone, 2-deoxy-D-glucose, potassium cyanide, rotenone), inhibit ATP-sensitive K-channels distributed in mitochondria (glibenclamide, 5-hydroxydecanoic acid) and inhibit the activity of proteinkinase C (chelerythrine), on the I-D relationship of follower potentials. The effects of depolarization on follower potentials were assessed by stimulating tissues with high potassium solution. Experiments were carried out mainly in the presence of nifedipine which minimized the movements of muscles with no modulation of follower potentials. Cycropiazonic acid and caffeine reduced the slope of I-D relationship, with associated reduction of the duration and frequency of follower potentials. 2-Aminoethoxydiphenyl borate reduced the duration and amplitude and increased the frequency of follower potentials, with depolarization of the membrane, and the effects were simulated by high potassium solution. m-Chlorophenyl hydrazone, potassium cyanide, 2-deoxy-D-glucose, rotenone, 5-hydroxydecanoic acid and glibenclamide reduced the slope of I-D relationship, with associated reduction of the frequency of follower potentials. Chelerythrine did not modulate the slope of I-D relationship, with reduced frequency of follower potentials. It seemed likely that the amount of Ca(2+) released from the internal stores and also mitochondrial function had causal relationship to the duration of pacemaker potentials, suggesting that internal Ca-stores and mitochondria are taking the central role for determining the duration of the pacemaker activity. Proteinkinase C did not seem to participate to the function of mitochondria and internal Ca(2+) stores.
Collapse
Affiliation(s)
- Yuhsuke Shigemasa
- Department of Cell Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan
| | | | | | | |
Collapse
|
66
|
Kim BJ, Nam JH, Kim SJ. Effects of transient receptor potential channel blockers on pacemaker activity in interstitial cells of Cajal from mouse small intestine. Mol Cells 2011; 32:153-60. [PMID: 21607648 PMCID: PMC3887672 DOI: 10.1007/s10059-011-1019-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Revised: 04/25/2011] [Accepted: 05/02/2011] [Indexed: 11/25/2022] Open
Abstract
The interstitial cells of Cajal (ICCs) are pacemakers in the gastrointestinal tract and transient receptor potential melastatin type 7 (TRPM7) is a candidate for pacemaker channels. The effect of the 5-lipoxygenase (5-LOX) inhibitors NDGA, AA861, MK886 and zileuton on pacemaking activity of ICCs was examined using the whole cell patch clamp technique. NDGA and AA861 decreased the amplitude of pacemaker potentials in ICC clusters, but the resting membrane potentials displayed little change, respectively. Also, perfusing NDGA and AA861 into the bath reduced both inward current and outward current in TRPM7-like current in single ICC, respectively. But, they had no effects on Ca(2+) activated Cl(-) currents. The 5-LOX inhibitors MK886 and zileuton were, however, ineffective in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC, respectively. A specific TRPC3 inhibitor, pyrazole compound (Pyr3), and a specific TRPM4 inhibitor, 9-phenanthrol, had no effects in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC. These results suggest that, among the tested 5-LOX inhibitors, NDGA and AA861 modulate the pacemaker activities of the ICCs, and that the TRPM7 channel can affect intestinal motility.
Collapse
Affiliation(s)
- Byung Joo Kim
- Division of Longevity and Biofunctional Medicine, Pusan National University School of Korean Medicine, Yangsan 626-870, Korea
- These authors contributed equally to this work
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Kyungju 780-714, Korea
- These authors contributed equally to this work
| | - Seon Jeong Kim
- Center for Bio-Artificial Muscle and Department of Biomedical Engineering, Hanyang University, Seoul 133-791, Korea
| |
Collapse
|
67
|
Jin YR, Jin J, Piao XX, Jin NG. The effect of Taraxacum officinale on gastric emptying and smooth muscle motility in Rodents. Neurogastroenterol Motil 2011; 23:766-e333. [PMID: 21453412 DOI: 10.1111/j.1365-2982.2011.01704.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Taraxacum officinale (TO) is a traditional herbal medicine that has been widely used for abdominal illnesses. However, the efficacy and the mechanism of TO on gastric emptying (GE) and smooth muscle motility are unknown. METHODS Ethyl acetate fraction (EA), n-butanol fraction (BF), and aqueous fraction (AF) were prepared in succession from 70% ethanol extract (EE) of TO using solvent polarity chromatography. Phenol red meal was adopted to estimate GE in mice. A polygraph was used to measure the smooth muscle motility in rats. KEY RESULTS The percentage of GE was 48.8 ± 6.1% (vehicle control), 75.3 ± 6.5% (cisapride positive control), 68.0±6.7% (EE), 53.3±6.0% (EA), 54.1±6.3% (AF), and 86.0±6.5% (BF). Thus, BF was determined to be most effective in accelerating GE. This stimulatory effect of BF on GE was also supported by the observation that BF increased spontaneous contraction of gastric fundus and antrum and decreased the spontaneous motility of pyloric sphincter in vitro. Atropine blocked the stimulatory effect of BF on GE, whereas phentolamine and propranolol had no effect. CONCLUSIONS & INFERENCES BF seems to be a promising prokinetic agent. BF-induced increase in the contraction of fundus and antrum contributes to an increase in the intra-gastric pressure. BF-induced decrease in the motility of pyloric sphincter contributes to a decrease in the resistance of food from the stomach to the small intestine. The acceleration of GE by BF is likely to be exerted through cholinergic stimulation.
Collapse
Affiliation(s)
- Y-R Jin
- Department of Gastroenterology and Hepatology, The Affiliated Hospital of Yanbian University College of Medicine, Yanji, Jilin Province, China.
| | | | | | | |
Collapse
|
68
|
Lees-Green R, Du P, O'Grady G, Beyder A, Farrugia G, Pullan AJ. Biophysically based modeling of the interstitial cells of cajal: current status and future perspectives. Front Physiol 2011; 2:29. [PMID: 21772822 PMCID: PMC3131535 DOI: 10.3389/fphys.2011.00029] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 06/13/2011] [Indexed: 12/29/2022] Open
Abstract
Gastrointestinal motility research is progressing rapidly, leading to significant advances in the last 15 years in understanding the cellular mechanisms underlying motility, following the discovery of the central role played by the interstitial cells of Cajal (ICC). As experimental knowledge of ICC physiology has expanded, biophysically based modeling has become a valuable tool for integrating experimental data, for testing hypotheses on ICC pacemaker mechanisms, and for applications in in silico studies including in multiscale models. This review is focused on the cellular electrophysiology of ICC. Recent evidence from both experimental and modeling domains have called aspects of the existing pacemaker theories into question. Therefore, current experimental knowledge of ICC pacemaker mechanisms is examined in depth, and current theories of ICC pacemaking are evaluated and further developed. Existing biophysically based ICC models and their physiological foundations are then critiqued in light of the recent advances in experimental knowledge, and opportunities to improve these models are identified. The review concludes by examining several potential clinical applications of biophysically based ICC modeling from the subcellular through to the organ level, including ion channelopathies and ICC network degradation.
Collapse
Affiliation(s)
- Rachel Lees-Green
- Auckland Bioengineering Institute, The University of Auckland Auckland, New Zealand
| | | | | | | | | | | |
Collapse
|
69
|
Chronic constipation: lessons from animal studies. Best Pract Res Clin Gastroenterol 2011; 25:59-71. [PMID: 21382579 DOI: 10.1016/j.bpg.2010.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 11/23/2010] [Accepted: 12/15/2010] [Indexed: 01/31/2023]
Abstract
Chronic constipation is a highly debilitating condition, affecting a significant proportion of the community. The burden to the health care system and impact on individual patients quality of life is immense. Unfortunately, the aetiology underlying chronic constipation is poorly understood and animal models are being used increasingly to investigate possible intrinsic neurogenic and myogenic mechanisms leading to relevant colonic sensori-motor dysfunction. Recently, major advances have been made in our understanding of the mechanisms that underlie propagating contractions along the large intestine, such as peristalsis and colonic migrating motor complexes in laboratory animals, particularly in guinea-pigs and mice. The first recordings of cyclical propagating contractions along the isolated whole human colon have now also been made. This review will highlight some of these advances and how impairments to these motility patterns may contribute to delayed colonic transit, known to exist in a proportion of patients with chronic constipation.
Collapse
|
70
|
Du P, O'Grady G, Davidson JB, Cheng LK, Pullan AJ. Multiscale modeling of gastrointestinal electrophysiology and experimental validation. Crit Rev Biomed Eng 2011; 38:225-54. [PMID: 21133835 DOI: 10.1615/critrevbiomedeng.v38.i3.10] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Normal gastrointestinal (GI) motility results from the coordinated interplay of multiple cooperating mechanisms, both intrinsic and extrinsic to the GI tract. A fundamental component of this activity is an omnipresent electrical activity termed slow waves, which is generated and propagated by the interstitial cells of Cajal (ICCs). The role of ICC loss and network degradation in GI motility disorders is a significant area of ongoing research. This review examines recent progress in the multiscale modeling framework for effectively integrating a vast range of experimental data in GI electrophysiology, and outlines the prospect of how modeling can provide new insights into GI function in health and disease. The review begins with an overview of the GI tract and its electrophysiology, and then focuses on recent work on modeling GI electrical activity, spanning from cell to body biophysical scales. Mathematical cell models of the ICCs and smooth muscle cell are presented. The continuum framework of monodomain and bidomain models for tissue and organ models are then considered, and the forward techniques used to model the resultant body surface potential and magnetic field are discussed. The review then outlines recent progress in experimental support and validation of modeling, and concludes with a discussion on potential future research directions in this field.
Collapse
Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, The University of Auckland, New Zealand.
| | | | | | | | | |
Collapse
|
71
|
You CZ, Dong R, Sun JJ, Xiao JQ, Qu HC, Du MH, Huang HQ, Tang WH. Pyloric resection and delayed gastric liquid emptying in rats. Dig Dis Sci 2011; 56:49-58. [PMID: 20431948 DOI: 10.1007/s10620-010-1238-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2009] [Accepted: 04/06/2010] [Indexed: 01/19/2023]
Abstract
BACKGROUND Surgical resection of the distal stomach impairs gastric emptying. Generally, pylorus and the antrum are removed in the distal gastrectomy, however, the pylorus is removed individually under specific circumstances. We focus on the relation between the pyloric resection and the gastric liquid emptying. AIMS The present investigation aimed to explore the pylorectomy how to influence gastric liquid emptying in rats. METHODS Pylorectomy and end-to-end gastroduodenal anastomosis were conducted in rats. Electrodes were implanted in the gastrointestinal serosal surface near the stoma. Total stomach, proximal stomach, distal stomach and duodenal liquid emptying, myoelectricities in the gastrointestinal tract near the stoma, and structures were examined with scintigraphy, electrode recording in vivo, and electron microscopy, respectively. RESULTS Delayed total stomach and distal stomach emptying were found in pylorectomy rats (p<0.001). However, there was no difference in the proximal stomach and the duodenal liquid emptying compared to the controls (p>0.05). The myoelectricity of 3-5 cpm (cycles/min) in antrum and 10-12 cpm in duodenum were found in the controls and no retrograde or antegrade myoelectricities were recorded in the duodenum and antrum. High-frequency myoelectricities (tachygastria) were recorded in the antrum near the stoma (p<0.01), the retrograde and antegrade myoelectricities propagating through the stoma were recorded, and the regenerated interstitial cells of Cajal were found in stoma under electron microscope observation in pylorectomy rat. CONCLUSIONS The gastroduodenal incoordination and abnormal myoelectricity related to impaired contraction in the antrum caused the delayed liquid gastric emptying in pylorectomy rats.
Collapse
Affiliation(s)
- Cheng-Zhong You
- Department of General Surgery, Zhong-Da Hospital, and Department of Physiology, Southeast University School of Medicine, 210009, Nanjing, China
| | | | | | | | | | | | | | | |
Collapse
|
72
|
Deng JJ. Acupuncture improves the repair and regeneration of interstitial cells of Cajal in rats after enteroenterostomy. Shijie Huaren Xiaohua Zazhi 2010; 18:3863-3868. [DOI: 10.11569/wcjd.v18.i36.3863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the mechanism by which acupuncture promotes intestinal motility.
METHODS: Thirty Sprague-Dawley rats were randomly divided into blank group, model group (receiving colocolic anastomosis) and acupuncture group. The acupuncture group underwent acupuncture at Zusanli, Sanyinjiao and Taichong daily for three continuous days. After acupuncture treatment, defecation was observed and intestinal propulsive rate was measured. Tissue samples of the colon which was 2 cm below the caecum were taken to observe the ultrastructure of interstitial cells of Cajal (ICC) and the Ache-ICC-SMC network.
RESULTS: In the acupuncture group, the time to first postoperative passage of feces was shortened and intestinal propulsive rate was improved compared with the model group [(2.00 ± 0.47) d vs (2.50 ± 0.53) d, (66.30 ± 4.21)% vs (46.33 ± 5.56)% , both P < 0.05]. Compared with the blank group, the damage of ICC ultrastructure in the model group was more significant while that in the acupuncture group was milder. In the model group, the ENS-ICC-SMC structure was disorganized, and the number of ICC and their fluorescence intensity were greatly decreased compared with the blank group [(18.67 ± 6.11) vs(32.33 ± 5.51), (35.00 ± 9.54) vs (58.67 ± 10.21), both P < 0.05]. In contrast, in the acupuncture group, the damage of the network structure was milder, and the number of ICC and their fluorescence intensity were increased compared with the model group [(30.33 ± 3.21) vs (18.67 ± 6.11), (56.67 ± 9.45) vs (35.00 ± 9.54), both P < 0.05]. Similar results were also obtained for the number of VAChT-positive nerve fibres [(18.67 ± 3.79) vs (20.67 ± 3.21), (20.33 ± 5.13) vs (34.67 ± 6.81), (23.00 ± 4.58) vs (18.67 ± 3.79), (36.00 ± 8.19) vs (20.33 ± 5.13), all P < 0.05].
CONCLUSION: Acupuncture can improve intestinal motility in rats after abdominal operation perhaps by improving the repair and regeneration of ICC.
Collapse
|
73
|
Abstract
Interstitial cells of Cajal (ICC) are important players in the symphony of gut motility. They have a very significant physiological role orchestrating the normal peristaltic activity of the digestive system. They are the pacemaker cells in gastrointestinal (GI) muscles. Absence, reduction in number or altered integrity of the ICC network may have a dramatic effect on GI system motility. More understanding of ICC physiology will foster advances in physiology of gut motility which will help in a future breakthrough in the pharmacological interventions to restore normal motor function of GI tract. This mini review describes what is known about the physiologic function and role of ICCs in GI system motility and in a variety of GI system motility disorders.
Collapse
|
74
|
Huang X, Zhao D, Wang ZY, Zhang ML, Yan ZQ, Han YF, Xu WX, Jiang ZL. The properties of spontaneous transient inward currents of interstitial cells in rabbit portal vein. Eur J Pharmacol 2010; 643:63-9. [PMID: 20599931 DOI: 10.1016/j.ejphar.2010.06.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 05/18/2010] [Accepted: 06/07/2010] [Indexed: 10/19/2022]
Abstract
The present study was designed to investigate the properties of spontaneous transient inward currents generated by interstitial cells (ICs) in the rabbit portal vein. Single ICs were freshly isolated from smooth muscle of the rabbit portal vein enzymetically. Using whole-cell patch clamp techniques, the spontaneous transient inward currents (STICs) were recorded at -60 mV of holding potential in freshly dispersed ICs. Both gadolinium, a non-selective cation channel inhibitor, and niflumic acid, a calcium-activated chloride channel blocker, abolished the inward currents. Replacement of external Na(+) with N-methyl-d-glucamine (NMDG(+)) also blocked the inward currents. The inward currents were abolished by caffeine, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), thapsigargin and ryanodine, but were partly inhibited by 2-aminoethoxydiphenyl borate (2-APB). W-7, a calmodulin inhibitor, increased the amplitude of the inward currents. These results suggest that non-selective cation channels are involved in the generation of the spontaneous transient inward currents recorded from ICs. The currents are regulated by intracellular calcium and calmodulin. But in the present study, the involvement of the calcium-activated chloride channels in the generation of the currents cannot be excluded.
Collapse
Affiliation(s)
- Xu Huang
- Department of Physiology, School of Medicine, Shanghai Jiao Tong University, Shanghai 200240, China
| | | | | | | | | | | | | | | |
Collapse
|
75
|
Takaki M, Suzuki H, Nakayama S. Recent advances in studies of spontaneous activity in smooth muscle: ubiquitous pacemaker cells. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2010; 102:129-35. [PMID: 20553741 DOI: 10.1016/j.pbiomolbio.2010.05.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Accepted: 05/19/2010] [Indexed: 02/08/2023]
Abstract
The general and specific properties of pacemaker cells, including Kit-negative cells, that are distributed in gastrointestinal, urethral and uterine smooth muscle tissues, are discussed herein. In intestinal tissues, interstitial cells of Cajal (ICC) are heterogeneous in both their forms and roles. ICC distributed in the myenteric layer (ICC-MY) act as primary pacemaker cells for intestinal mechanical and electrical activity. ICC distributed in muscle bundles play a role as mediators of signals from autonomic nerves to smooth muscle cells. A group of ICC also appears to act as a stretch sensor. Intracellular Ca2+ dynamics play a crucial role in ICC-MY pacemaking; intracellular Ca2+ ([Ca2+](i)) oscillations periodically activate plasmalemmal Ca2+-activated ion channels, such as Ca2+-activated Cl(-) channels and/or non-selective cation channels, although the relative contributions of these channels are not defined. With respect to gut motility, both the ICC network and enteric nervous system, including excitatory and inhibitory enteric neurons, play an essential role in producing highly coordinated peristalsis.
Collapse
Affiliation(s)
- Miyako Takaki
- Department of Physiology II, Nara Medical University, 840 Shijo-cho, Kashihara 634-8521, Japan.
| | | | | |
Collapse
|
76
|
Huang X, Zhao D, Wang ZY, Zhang ML, Yan ZQ, Han YF, Lu HL, Xu WX, Jiang ZL. Spontaneous rhythmic inward currents recorded in interstitial cells of rabbit portal vein. Cell Biochem Biophys 2010; 57:77-85. [PMID: 20473644 DOI: 10.1007/s12013-010-9085-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
It is now well established that smooth muscle of the portal vein exhibits spontaneous rhythmic contraction in vitro. The present study was designed to investigate the pacemaking mechanism(s) underlying the spontaneous rhythmic contractions in the rabbit portal vein (RPV). Using whole-cell patch clamp techniques, spontaneous inward currents were recorded at -60 mV of holding potential in freshly dispersed c-Kit immunopositive interstitial cells (ICs) isolated from sections of RPV. The inward currents were abolished by caffeine, FCCP, thapsigargin, and ryanodine, but were partially inhibited by 2-APB. Both gadolinium, a non-selective cation channel inhibitor, and niflumic acid, a chloride channel blocker, inhibited the inward currents completely. Replacement of external Na(+) with NMDG(+) also blocked the inward currents. W-7, a calmodulin inhibitor, increased both the amplitude and frequency of the inward currents. Taken together, these results indicate that non-selective cationic channels are involved in the generation of spontaneous inward currents recorded from ICs. Intracellular calcium concentration and calmodulin regulate the spontaneous inward currents, which may account for spontaneous rhythmic contraction in the RPV, but a role of chloride channels may not be excluded in the present study.
Collapse
Affiliation(s)
- Xu Huang
- Department of Physiology, School of Medicine, Shanghai Jiao Tong University, 800 Dongchuan Road, Minhang, Shanghai, 200240, China
| | | | | | | | | | | | | | | | | |
Collapse
|
77
|
Bone marrow derivation of interstitial cells of cajal in small intestine following intestinal injury. J Biomed Biotechnol 2010; 2010:164986. [PMID: 20396598 PMCID: PMC2854535 DOI: 10.1155/2010/164986] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 12/24/2009] [Accepted: 01/27/2010] [Indexed: 12/14/2022] Open
Abstract
Interstitial cells of Cajal (ICCs) in gastrointestinal tract are specialized cells serving as pacemaker cells. The origin of ICCs is currently not fully characterized. In this work, we aimed to study whether bone marrow-derived cells (BMDCs) could contribute to the origin of ICCs in the muscular plexus of small intestine using GFP-C57BL/6 chimeric mice.Engraftment of BMDCs in the intestine was investigated for GFP expression. GFP positive bone marrow mononuclear cells reached a proportion of 95.65% ± 3.72% at different times in chimerism. Donor-derived cells distributed widely in all the layers of the gastrointestinal tract. There were GFP positive BMDCs in the myenteric plexus, which resembled characteristics of ICCs, including myenteric location, c-Kit positive staining, and ramified morphology. Donor-derived ICCs in the myenteric plexus contributed to a percentage ranging 9.25% ± 4.9% of all the ICCs in the myenteric plexus. In conclusion, here we described that donor-derived BMDCs might differentiate into gastrointestinal ICCs after radiation injury, which provided an alternative source for the origin of the ICCs in the muscular plexus of adult intestine. These results further identified the plasticity of BMDCs and indicated therapeutic implications of BMDCs for the gastrointestinal dysmotility caused by ICCs disorders.
Collapse
|
78
|
Wang ZY, Xu WX. Advances in research on pacemaking function of gastrointestinal smooth muscle cells. Shijie Huaren Xiaohua Zazhi 2010; 18:319-323. [DOI: 10.11569/wcjd.v18.i4.319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Gastrointestinal smooth muscle has spontaneous contractile activity, which is very important to digestion and absorption function. However, the pacemaking mechanism in gastrointestinal smooth muscle is still not clear. In this article, we review the recent advances in research on the mechanisms underlying gastrointestinal pacemaker activity. We summarize the classification, function and pacemaking mechanisms of pacemaker cells, and the relationship between pacemaker cells and gastrointestinal motility dysfunction. As abnormal pacemaking activity is often associated with gastrointestinal motility dysfunction, it is of great clinical significance to clarify the pacemaking mechanisms in the gastrointestinal tract.
Collapse
|
79
|
Lin Z, Sarosiek I, Forster J, Damjanov I, Hou Q, McCallum RW. Association of the status of interstitial cells of Cajal and electrogastrogram parameters, gastric emptying and symptoms in patients with gastroparesis. Neurogastroenterol Motil 2010; 22:56-61, e10. [PMID: 19614868 DOI: 10.1111/j.1365-2982.2009.01365.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Our goal was to investigate associations between the status of interstitial cells of Cajal (ICC) and electrogastrogram (EGG) parameters, gastric emptying and symptoms in a large cohort of patients with gastroparesis. Forty-one patients with refractory gastroparesis who were referred for gastric electrical stimulation (GES) underwent full thickness gastric (antrum) biopsy during the surgery to place the GES device. The biopsy samples were stained with c-kit and scored for the presence of ICC based on criteria obtained from 10 controls. All patients underwent EGG recordings, a 4-h standardized scintigraphic gastric emptying study and symptom assessment prior to the surgery. Based on antral biopsy, 15 patients (36%) had almost no ICC (ICC- group) and 26 patients had adequate cell numbers (ICC+ group). EGG recordings in the ICC- group displayed significantly less normal slow waves than in the ICC+ group both in the fasting and fed states. Tachygastria in the ICC- group was significantly more than in the ICC+ group both in the fasting (32 +/- 8%vs 11 +/- 2%) and fed states (27 +/- 9%vs 12 +/- 2%). There was no statistical difference in gastric emptying, symptom severity of gastroparesis, aetiology, age and gender between the two groups. Severely depleted ICC occurs in up to 36% of gastroparetic patients and significantly correlates with an abnormal EGG. Severely depleted ICC does not correlate with the severity of gastroparesis as assessed by gastric emptying or symptom status but did result in a poorer symptomatic response to GES. These data suggest that the EGG may have a role for predicting ICC status during clinical evaluation of gastroparetic patients.
Collapse
Affiliation(s)
- Z Lin
- Department of Medicine, University of Kansas Medical Center, Kansas City, KS, USA
| | | | | | | | | | | |
Collapse
|
80
|
Kim BJ, Park KJ, Kim HW, Choi S, Jun JY, Chang IY, Jeon JH, So I, Kim SJ. Identification of TRPM7 channels in human intestinal interstitial cells of Cajal. World J Gastroenterol 2009; 15:5799-804. [PMID: 19998500 PMCID: PMC2791272 DOI: 10.3748/wjg.15.5799] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the characteristics of slow electrical waves and the presence of transient receptor potential melastatin-type 7 (TRPM7) in the human gastrointestinal (GI) tract.
METHODS: Conventional microelectrode techniques were used to record intracellular electrical responses from human GI smooth muscle tissue. Immunohistochemistry was used to identify TRPM7 channels in interstitial cells of Cajal (ICCs).
RESULTS: The human GI tract generated slow electrical waves and had ICCs which functioned as pacemaker cells. Flufenamic acid, a nonselective cation channel blocker, and 2-APB (2-aminoethoxydiphenyl borate) and La3+, TRPM7 channel blockers, inhibited the slow waves. Also, TRPM7 channels were expressed in ICCs in human tissue.
CONCLUSION: These results suggest that the human GI tract generates slow waves and that TRPM7 channels expressed in the ICCs may be involved in the generation of the slow waves.
Collapse
|
81
|
van Helden DF, Laver DR, Holdsworth J, Imtiaz MS. Generation and propagation of gastric slow waves. Clin Exp Pharmacol Physiol 2009; 37:516-24. [PMID: 19930430 DOI: 10.1111/j.1440-1681.2009.05331.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. Mechanisms underlying the generation and propagation of gastrointestinal slow wave depolarizations have long been controversial. The present review aims to collate present knowledge on this subject with specific reference to slow waves in gastric smooth muscle. 2. At present, there is strong agreement that interstitial cells of Cajal (ICC) are the pacemaker cells that generate slow waves. What has been less clear is the relative role of primary types of ICC, including the network in the myenteric plexus (ICC-MY) and the intramuscular network (ICC-IM). It is concluded that both ICC-MY and ICC-IM are likely to serve a major role in slow wave generation and propagation. 3. There has been long-standing controversy as to how slow waves 'propagate' circumferentially and down the gastrointestinal tract. Two mechanisms have been proposed, one being action potential (AP)-like conduction and the other phase wave-based 'propagation' resulting from an interaction of coupled oscillators. Studies made on single bundle gastric strips indicate that both mechanisms apply with relative dominance depending on conditions; the phase wave mechanism is dominant under circumstances of rhythmically generating slow waves and the AP-like propagation is dominant when the system is perturbed. 4. The phase wave mechanism (termed Ca(2+) phase wave) uses cyclical Ca(2+) release as the oscillator, with coupling between oscillators mediated by several factors, including: (i) store-induced depolarization; (ii) resultant electrical current flow/depolarization through the pacemaker cell network; and (iii) depolarization-induced increase in excitability of downstream Ca(2+) stores. An analogy is provided by pendulums in an array coupled together by a network of springs. These, when randomly activated, entrain to swing at the same frequency but with a relative delay along the row giving the impression of a propagating wave. 5. The AP-like mechanism (termed voltage-accelerated Ca(2+) wave) propagates sequentially like a conducting AP. However, it is different in that it depends on regenerative store Ca(2+) release and resultant depolarization rather than regenerative activation of voltage-dependent channels in the cell membrane. 6. The applicability of these mechanisms to describing propagation in large intact gastrointestinal tissues, where voltage-dependent Ca(2+) entry is also likely to be functional, is discussed.
Collapse
Affiliation(s)
- Dirk F van Helden
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, Callaghan, New South Wales, Australia.
| | | | | | | |
Collapse
|
82
|
Kito Y, Sanders KM, Ward SM, Suzuki H. Interstitial cells of Cajal generate spontaneous transient depolarizations in the rat gastric fundus. Am J Physiol Gastrointest Liver Physiol 2009; 297:G814-24. [PMID: 19643953 PMCID: PMC2763808 DOI: 10.1152/ajpgi.00118.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Intracellular recordings were made from isolated circular muscle bundles of rat gastric fundus. The majority of cells generated an ongoing discharge of electrical activity that were <or=10 mV in amplitude (unitary potentials). A second pattern of electrical activity was recorded in less than 1% of all impalements. This electrical activity was characterized by high frequency, large amplitude spontaneous transient depolarizations (STDs) with a maximum rate of rise (dV/dt(max)) of 0.5 V/s. Injection of the fluorescent dye propidium iodide into cells and double labeling with an antibody against the Kit receptor revealed that unitary potentials were recorded from circular smooth muscle cells (CSMC), whereas STDs were generated by intramuscular interstitial cells of Cajal (ICC-IM). Sustained injection periods (>15 min) resulted in the spread of dye between CSMC, between ICC-IM, and between CSMC and ICC-IM. Two types of STDs were observed, regularly occurring continuous STDs and irregular noisy bursting STDs. The amplitude of STDs varied between the two types of STDs. Single units summed to develop STDs with a maximum amplitude of 30 mV. Sodium nitroprusside (3 microM) induced membrane hyperpolarization and abolished unitary potentials generated by CSMC. In contrast, the amplitude of STDs generated by ICC-IM was increased with membrane hyperpolarization. Hyperpolarization induced by pinacidil (10 microM) also increased the amplitude of STDs and enhanced dV/dt(max). These observations indicate that STDs generated in ICC-IM spread passively to the adjacent CSMC to evoke the discharge of unitary potentials in the gastric fundus.
Collapse
Affiliation(s)
- Yoshihiko Kito
- Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan.
| | - Kenton M. Sanders
- 2Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sean M. Ward
- 2Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Hikaru Suzuki
- 1Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan;
| |
Collapse
|
83
|
Nakamura E, Yokoi T, Fukuta H, Iida T, Tanaka Y, Yamamoto Y, Suzuki H. Hypoxia differentially modulates the activity of pacemaker and smooth muscle cells in the guinea pig stomach antrum. J Smooth Muscle Res 2009; 45:149-66. [PMID: 19783869 DOI: 10.1540/jsmr.45.149] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Effects of hypoxic solution (O(2) tension, 161 +/- 11 mmHg) on electrical responses of the membrane (slow waves), intracellular Ca(2+)-responses measured by Fura-2 fluorescence (Ca-transients) and isometric mechanical responses (phasic contraction) were observed in circular smooth muscles isolated from the guinea-pig stomach antrum. In normoxic solution (O(2) tension, 362 +/- 28 mmHg), muscle cells generated slow waves spontaneously, and switching to hypoxic solution caused an increase in frequency and decrease in duration of slow waves, with no significant change in the resting membrane potential. Hypoxia also reduced the amplitude and duration and increased the frequency of Ca-transients. The increase in frequency of slow waves by hypoxia was prevented by cyclopiazonic acid (CPA) but not by carbonyl cyanide m-chlorophenyl-hydrazone (CCCP), potassium cyanide (KCN) or low-Ca solution. The reduction by hypoxia of the duration of slow waves was prevented by CCCP or KCN but not by CPA or low-Ca solution. Hypoxia resulted in an increase in frequency and decrease in amplitude of phasic contractions, and the changes were prevented by CPA but not by CCCP. These results suggested that in antrum smooth muscle tissues, the increase in frequency of spontaneous activity by hypoxia is related to the enhanced function of the CPA-sensitive internal Ca-stores in pacemaker cells, while the inhibition in amplitude of phasic contractions by hypoxia may be mainly related to the decrease in Ca(2+) release from the CPA-sensitive internal stores in smooth muscle cells. It is concluded that in hypoxic solution, the function of internal Ca(2+) stores is enhanced in ICC-MY and is inhibited in smooth muscle cells in the guinea-pig stomach antrum.
Collapse
Affiliation(s)
- Eri Nakamura
- Department of Physiology, Nagoya City University, Mizuho-ku, Nagoya, Japan.
| | | | | | | | | | | | | |
Collapse
|
84
|
Zhu MH, Kim TW, Ro S, Yan W, Ward SM, Koh SD, Sanders KM. A Ca(2+)-activated Cl(-) conductance in interstitial cells of Cajal linked to slow wave currents and pacemaker activity. J Physiol 2009; 587:4905-18. [PMID: 19703958 DOI: 10.1113/jphysiol.2009.176206] [Citation(s) in RCA: 211] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Interstitial cells of Cajal (ICC) are unique cells that generate electrical pacemaker activity in gastrointestinal (GI) muscles. Many previous studies have attempted to characterize the conductances responsible for pacemaker current and slow waves in the GI tract, but the precise mechanism of electrical rhythmicity is still debated. We used a new transgenic mouse with a bright green fluorescent protein (copGFP) constitutively expressed in ICC to facilitate study of these cells in mixed cell dispersions. We found that ICC express a specialized 'slow wave' current. Reversal of tail current analysis showed this current was due to a Cl(-) selective conductance. ICC express ANO1, a Ca(2+)-activated Cl(-) channel. Slow wave currents are not voltage dependent, but a secondary voltage-dependent process underlies activation of these currents. Removal of extracellular Ca(2+), replacement of Ca(2+) with Ba(2+), or extracellular Ni(2+) (30 microm) blocked the slow wave current. Single Ca(2+)-activated Cl() channels with a unitary conductance of 7.8 pS were resolved in excised patches of ICC. These are similar in conductance to ANO1 channels (8 pS) expressed in HEK293 cells. Slow wave current was blocked in a concentration-dependent manner by niflumic acid (IC(50) = 4.8 microm). Slow wave currents are associated with transient depolarizations of ICC in current clamp, and these events were blocked by niflumic acid. These findings demonstrate a role for a Ca(2+)-activated Cl(-) conductance in slow wave current in ICC and are consistent with the idea that ANO1 participates in pacemaker activity.
Collapse
Affiliation(s)
- Mei Hong Zhu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | | | | | | | | | |
Collapse
|
85
|
Zhu MH, Kim TW, Ro S, Yan W, Ward SM, Koh SD, Sanders KM. A Ca(2+)-activated Cl(-) conductance in interstitial cells of Cajal linked to slow wave currents and pacemaker activity. J Physiol 2009. [PMID: 19703958 DOI: 10.1113/jphysiol.2009.176206.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Interstitial cells of Cajal (ICC) are unique cells that generate electrical pacemaker activity in gastrointestinal (GI) muscles. Many previous studies have attempted to characterize the conductances responsible for pacemaker current and slow waves in the GI tract, but the precise mechanism of electrical rhythmicity is still debated. We used a new transgenic mouse with a bright green fluorescent protein (copGFP) constitutively expressed in ICC to facilitate study of these cells in mixed cell dispersions. We found that ICC express a specialized 'slow wave' current. Reversal of tail current analysis showed this current was due to a Cl(-) selective conductance. ICC express ANO1, a Ca(2+)-activated Cl(-) channel. Slow wave currents are not voltage dependent, but a secondary voltage-dependent process underlies activation of these currents. Removal of extracellular Ca(2+), replacement of Ca(2+) with Ba(2+), or extracellular Ni(2+) (30 microm) blocked the slow wave current. Single Ca(2+)-activated Cl() channels with a unitary conductance of 7.8 pS were resolved in excised patches of ICC. These are similar in conductance to ANO1 channels (8 pS) expressed in HEK293 cells. Slow wave current was blocked in a concentration-dependent manner by niflumic acid (IC(50) = 4.8 microm). Slow wave currents are associated with transient depolarizations of ICC in current clamp, and these events were blocked by niflumic acid. These findings demonstrate a role for a Ca(2+)-activated Cl(-) conductance in slow wave current in ICC and are consistent with the idea that ANO1 participates in pacemaker activity.
Collapse
Affiliation(s)
- Mei Hong Zhu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | | | | | | | | | |
Collapse
|
86
|
Nakayama S, Ohishi R, Sawamura K, Watanabe K, Hirose K. Microelectrode array evaluation of gut pacemaker activity in wild-type and W/W(v) mice. Biosens Bioelectron 2009; 25:61-7. [PMID: 19576758 DOI: 10.1016/j.bios.2009.06.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2009] [Revised: 06/01/2009] [Accepted: 06/02/2009] [Indexed: 02/07/2023]
Abstract
Interstitial cells of Cajal in the myenteric plexus region (ICC-MyP) form a network and generate basal pacemaking electrical activity. This morphological feature leads us to believe that these cells may be essential for the coordinating actions of gastrointestinal (GI) motility. We aim to propose a new method for functional assessment of ICC electrical activity and its network. Field potentials in a approximately 1 mm(2) region were simultaneously measured using an 8x8 microelectrode array (MEA) with a polar distance of 150 microm. The extracellular solution contained nifedipine and tetrodotoxin (TTX) to suppress activities of smooth muscle cells and neurons, respectively. We compared spatial electrical activities between ileal muscle preparations from wild-type (WT) and W/W(v) mice. In spatio-temporal analyses, basal electrical activities were well synchronized with a propagation delay in WT, while those in W/W(v) were small in amplitude and irregular in occurrence. The power spectrum in WT had a prominent peak corresponding to the frequency of ICC-MyP pacemaker activity, while that of W/W(v) lacked it. Consequently, the ratio of the spectral power in 9.4-27.0 cpm was significantly larger in WT than in W/W(v). In conclusion, MEA measurements demonstrated that the network-forming ICC-MyP not only generates but also coordinates basal electrical activities. Disorders of GI motility based on morphological and functional impairments of ICC network with the range of several hundreds of micrometers, could be uncovered in future extensive studies.
Collapse
Affiliation(s)
- Shinsuke Nakayama
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan.
| | | | | | | | | |
Collapse
|
87
|
Kim YC, Suzuki H, Xu WX, Choi W, Kim SH, Lee SJ. Ca2+-activated K+ current in freshly isolated c-Kit positive cells in guinea-pig stomach. J Korean Med Sci 2009; 24:384-91. [PMID: 19543421 PMCID: PMC2698181 DOI: 10.3346/jkms.2009.24.3.384] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Accepted: 01/29/2008] [Indexed: 11/22/2022] Open
Abstract
This study was designed to isolate Ca2+-activated K+ current (I(KCa)) and elucidate its physiological significance in freshly isolated interstitial cells of Cajal (ICCs) of guinea-pig stomach. Single ICC was freshly isolated by enzymatically dissociating from myenteric border of gastric antrum free of circular muscles, and conventional whole-cell voltage clamp technique including immunohistochemical techniques were employed to characterize the cells: In myenteric border of gastric antrum, ICC-MY (ICCs from myenteric border) were detected by immunohistochemical reactivity, and single ICC-MY which has many branches was immunohistochemically c-Kit positive. Under K+-rich and 0.1 mM ethylene glycol-bis (2-aminoethyl ether)-N,N,N',N'-tetraacetic acid pipette solution, ICC produced spontaneous inward current (-256 +/- 92.2 pA). When step-depolarizing pulse from -80 to +80 mV was applied at holding potential (V(h)) of -80 mV, voltage-dependent outward currents were recorded with superimposed spontaneous transient outward currents (STOCs). Both STOCs and outward currents were reversibly affected by tetraethylammonium chloride (TEA) and iberiotoxin (IbTX); 2 mM TEA and 200 nM IbTX completely abolished STOCs and significantly inhibited outward K+ current over the whole potential range tested for current/voltage (I/V) relationship. In addition, TEA delayed repolarization phase of spontaneous inward current. The present results indicate the presence of I(KCa) in a single ICC, and it might be involved in regulation of repolarizing phase of spontaneous inward current in guinea-pig stomach.
Collapse
Affiliation(s)
- Young Chul Kim
- Department of Physiology, Chungbuk National University, College of Medicine, Cheongju, Korea.
| | | | | | | | | | | |
Collapse
|
88
|
Forrest AS, Hennig GW, Jokela-Willis S, Park CD, Sanders KM. Prostaglandin regulation of gastric slow waves and peristalsis. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1180-90. [PMID: 19359421 PMCID: PMC2697952 DOI: 10.1152/ajpgi.90724.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric emptying depends on functional coupling of slow waves between the corpus and antrum, to allow slow waves initiated in the gastric corpus to propagate to the pyloric sphincter and generate gastric peristalsis. Functional coupling depends on a frequency gradient where slow waves are generated at higher frequency in the corpus and drive the activity of distal pacemakers. Simultaneous intracellular recording from corpus and antrum was used to characterize the effects of PGE(2) on slow waves in the murine stomach. PGE(2) increased slow-wave frequency, and this effect was mimicked by EP(3), but not by EP(2), receptor agonists. Chronotropic effects were due to EP(3) receptors expressed by intramuscular interstitial cells of Cajal because these effects were not observed in W/W(V) mice. Although the integrated chronotropic effects of EP(3) receptor agonists were deduced from electrophysiological experiments, no clear evidence of functional uncoupling was observed with two-point electrical recording. Gastric peristalsis was also monitored by video imaging and spatiotemporal maps to study the impact of chronotropic agonists on propagating contractions. EP(3) receptor agonists increased the frequency of peristaltic contractions and caused ectopic sites of origin and collisions of peristaltic waves. The impact of selective regional application of chronotropic agonists was investigated by use of a partitioned bath. Antral slow waves followed enhanced frequencies induced by stimulation of the corpus, and corpus slow waves followed when slow-wave frequency was elevated in the antrum. This demonstrated reversal of slow-wave propagation with selective antral chronotropic stimulation. These studies demonstrate the impact of chronotropic agonists on regional intrinsic pacemaker frequency and integrated gastric peristalsis.
Collapse
Affiliation(s)
- Abigail S. Forrest
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Grant W. Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sari Jokela-Willis
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Chong Doo Park
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| |
Collapse
|
89
|
Domae K, Hashitani H, Suzuki H. Regional differences in the frequency of slow waves in smooth muscle of the guinea-pig stomach. J Smooth Muscle Res 2009; 44:231-48. [PMID: 19234377 DOI: 10.1540/jsmr.44.231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The frequency of slow waves recorded from circular muscle bundles with attached longitudinal muscle (intact muscle) was compared with that of slow potentials recorded from isolated circular muscle bundles (isolated muscle) from the guinea-pig stomach. In intact muscle preparations, slow waves were generated in the corpus, antrum and pylorus with a higher frequency in the corpus (about 5 min(-1)) than the other regions (about 2 min(-1) in antrum, about 1.5 min(-1) in pylorus). The resting potential amplitude was graded across the stomach, at about -50 mV in the fundus, -60 mV in the corpus, -65 mV in the antrum and -70 mV in the pylorus. A similar distribution of resting membrane potential and slow potential frequency was also observed in isolated muscle bundles from the different regions. Caffeine (1 mM) abolished slow waves in some corpus preparations and inhibited the 2nd component of slow waves in the antrum and pylorus, and also abolished slow potentials in isolated muscle preparations from any region of the stomach. This suggests that myenteric interstitial cells of Cajal (ICC-MY) are heterogeneously distributed in the stomach (pylorus, antrum and part of the corpus regions), with a homogeneous distribution of muscular interstitial cells of Cajal (ICC-IM) within the circular muscle bundles. The frequency of slow potentials in smooth muscle isolated from any region of the stomach changed linearly in response to membrane potential changes produced by either current injection or high potassium solutions. The frequency of slow potentials after setting the membrane potential at -60 mV was larger in the corpus than the antrum, suggesting that the high frequency discharge of corpus muscle is produced by the low membrane potential and additional unidentified factors. We suggest that the regional difference in slow wave discharge is produced mainly by ICC-IM, and the role of ICC-MY may be little, if any.
Collapse
Affiliation(s)
- Kazumasa Domae
- Department of Physiology, Nagoya City University Medical School, Japan
| | | | | |
Collapse
|
90
|
Sanmiguel CP, Ito Y, Hagiike M, Conklin JL, Lalezari D, Soffer EE. The effect of eating on lower esophageal sphincter electrical activity. Am J Physiol Gastrointest Liver Physiol 2009; 296:G793-7. [PMID: 19196951 DOI: 10.1152/ajpgi.90369.2008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Electrical activity of the lower esophageal sphincter (LES) has been recorded mainly in vitro and in anesthetized animals. Swallowing produces relaxation of the LES, followed by its contraction. These changes should be associated with changes in LES electrical activity. To determine whether changes in LES electrical activity can be used to recognize the beginning of a meal, four dogs were implanted with two electrodes in the longitudinal axis of the LES. The electrodes were connected to an implantable device for recording of electrical activity. After recovery, dogs underwent two experiments: 1) combined recordings of LES electrical activity and esophageal manometry to test the effect of dry swallows, water, and solid food swallows on LES electrical activity and 2) telemetric recording of LES electrical activity during a standard meal. All amplitudes were in mV, means+/-SD, ANOVA, P<0.05. In experiment 1, an increase in the amplitude of LES electrical activity was associated with the substance being swallowed, i.e., at rest: 0.31+/-0.06; dry swallows: 0.6+/-.0.1; water: 0.67+/-0.12; solid food: 1.06+/-0.17, P<0.001. In experiment 2, there was a pronounced and characteristic increase in amplitude of LES electrical activity during feeding, 0.26+/-0.1; during fasting, 0.99+/-0.23; while eating, 0.31+/-0.1 postprandial, P<0.001. In conclusion, the beginning and duration of a meal are identified by distinct, easily recognizable changes in the amplitude of LES electrical activity. These changes depend on the type of the substance being swallowed and are most prominent with solid food. Changes in LES electrical activity can potentially be used for automatic eating detection.
Collapse
Affiliation(s)
- Claudia P Sanmiguel
- Gastrointestinal Motility Program, Department of Minimally Invasive Surgery, Cedars Sinai Medical Center, 8730 Alden Dr., Thalians Bldg., 2nd Floor East, Los Angeles, CA 90048, USA
| | | | | | | | | | | |
Collapse
|
91
|
α1-adrenoceptor modulation of spontaneous electrical waveforms in the guinea-pig prostate. Eur J Pharmacol 2009; 608:62-70. [DOI: 10.1016/j.ejphar.2009.02.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 01/16/2009] [Accepted: 02/01/2009] [Indexed: 11/18/2022]
|
92
|
Tanaka C, Domae K, Hashitani H, Suzuki H. Modulation of slow waves by transmural nerve stimulation of smooth muscle tissue isolated from the corpus of the guinea-pig stomach. J Smooth Muscle Res 2009; 45:109-24. [DOI: 10.1540/jsmr.45.109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Chiharu Tanaka
- Department of Physiology, Nagoya City University Medical School
| | - Kazumasa Domae
- Department of Physiology, Nagoya City University Medical School
| | | | - Hikaru Suzuki
- Department of Physiology, Nagoya City University Medical School
| |
Collapse
|
93
|
Kim YC, Suzuki H, Xu WX, Hashitani H, Choi W, Yun HY, Park SM, Youn SJ, Lee SJ, Lee SJ. Voltage-dependent Ca Current Identified in Freshly Isolated Interstitial Cells of Cajal (ICC) of Guinea-pig Stomach. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:323-30. [PMID: 19967074 DOI: 10.4196/kjpp.2008.12.6.323] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The properties of voltage dependent Ca(2+) current (VDCC) were investigated in interstitial cells of Cajal (ICC) distributed in the myenteric layer (ICC-MY) of guinea-pig antrum. In tissue, ICC-MY showed c-Kit positive reactions and produced driving potentials with the amplitude and frequency of about 62 mV and 2 times min(-1), respectively, in the presence of 1 microM nifedipine. Single ICC-MY isolated by enzyme treatment also showed c-Kit immunohistochemical reactivity. These cells were also identified by generation of spontaneous inward current under K(+) -rich pipette solution. The voltage clamp experiments revealed the amplitude of - 329 pA inward current at irregular frequency. With Cs(+)-rich pipette solution at V(h)=-80 mV, ICC-MY produced voltage-dependent inward currents (VDIC), and nifedipine (1 microM) blocked VDIC. Therefore, we successfully isolated c-Kit positive single ICC from guinea-pig stomach, and found that ICC-MY potently produced dihydropiridine sensitive L-type voltage-dependent Ca(2+) currents (VDCC(L)).
Collapse
Affiliation(s)
- Young Chul Kim
- Department of Physiology, Chungbuk National University, College of Medicine, Cheongju 361-763, Korea
| | | | | | | | | | | | | | | | | | | |
Collapse
|
94
|
Hirst GDS, Hashitani H, Suzuki H. Cellular mechanism of the voltage-dependent change in slow potentials generated in circular smooth muscle of the guinea-pig gastric corpus. J Physiol 2008; 586:5521-36. [PMID: 18818248 PMCID: PMC2655369 DOI: 10.1113/jphysiol.2008.160531] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Accepted: 09/24/2008] [Indexed: 12/22/2022] Open
Abstract
The cellular mechanism of the voltage-dependent properties of slow potentials were investigated in single bundles of circular smooth muscle isolated from the gastric corpus of guinea-pig using conventional microelectrode recordings. Hyperpolarization of the membrane by current injection decreased the frequency and increased the amplitude of slow potentials linearly. At potentials negative of -80 mV, slow potential generation was abolished and a periodic generation of clustered unitary potentials was evident. Application of cyclopiazonic acid (CPA, 20 microM) or thapsigargin (1 microM; inhibitors of Ca(2+)-ATPase), carbonyl cyanide m-chlorophenyl hydrazone (CCCP, 0.1 microM; mitochondrial protonophore) or 2-aminoethoxydiphenyl borate (2-APB, 20 microM; inhibitor of IP(3) receptor-mediated Ca(2+) release) depolarized the membrane and reduced or inhibited the amplitude and frequency of slow potentials: repolarization of the membrane to the resting level by current injection resulted in a recovery of the amplitude of slow potentials in the presence of CPA or CCCP, but not 2-APB. The slow potentials abolished by thapsigargin did not recover upon membrane repolarization. The altered frequency of slow potentials by 2-APB, CPA or CCCP was not reversed by membrane repolarization to control potentials. Depolarization of the membrane by about 10 mV with high-potassium solution also reduced the amplitude and increased the frequency of slow potentials in a manner restored by repolarization to control potentials upon current injection, suggesting that membrane depolarization did not affect the voltage dependency of pacemaker activity. The results indicate that in corpus circular muscles the voltage dependency of the frequency and amplitude of slow potentials requires a functional Ca(2+) store and mitochondria.
Collapse
Affiliation(s)
- G D S Hirst
- Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan
| | | | | |
Collapse
|
95
|
Kilic A, Luketich JD, Landreneau RJ, Owens SR, Krasinskas AM, Schuchert MJ. Alterations in the density of interstitial cells of Cajal in achalasia. Dig Dis Sci 2008; 53:1488-92. [PMID: 18030621 DOI: 10.1007/s10620-007-0053-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 09/26/2007] [Indexed: 12/09/2022]
Abstract
The aim of this study was to assess the quantity of interstitial cells of Cajal (ICC) in the lower esophageal sphincter (LES) in achalasia. LES muscle was obtained from 11 achalasia and nine esophageal cancer (control) patients during surgery. Immunohistochemistry was performed and average cell counts per high-power field (HPF) were obtained. Overall, more ICC were observed in achalasia (median = 14.0 cells/HPF; range = 0-22.6 cells/HPF) as compared with controls (median = 6.2 cells/HPF; range = 1.6-10.8 cells/HPF) (P = 0.047). There were two subsets of findings within the achalasia group: 8/11(73%) had an increased quantity of ICC (median = 17.1 cells/HPF; range = 11.6-22.6; P = 0.015) as compared with controls, whereas the remaining 3/11(27%) had a paucity of ICC (median = 0 cells/HPF; range = 0-2; P = 0.02). ICC levels were positively correlated with age of the patient (P = 0.043). Our study demonstrates that subsets of abnormal ICC levels are observed in idiopathic achalasia of the esophagus.
Collapse
Affiliation(s)
- Arman Kilic
- Heart, Lung, and Esophageal Surgery Institute, University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA
| | | | | | | | | | | |
Collapse
|
96
|
Hashitani H, Hayase M, Suzuki H. Effects of imatinib mesylate on spontaneous electrical and mechanical activity in smooth muscle of the guinea-pig stomach. Br J Pharmacol 2008; 154:451-9. [PMID: 18414381 DOI: 10.1038/bjp.2008.91] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND AND PURPOSE Effects of imatinib mesylate, a Kit receptor tyrosine kinase inhibitor, on spontaneous activity of interstitial cells of Cajal (ICC) and smooth muscles in the stomach were investigated. EXPERIMENTAL APPROACH Effects of imatinib on spontaneous electrical and mechanical activity were investigated by measuring changes in the membrane potential and tension recorded from smooth muscles of the guinea-pig stomach. Its effects on spontaneous changes in intracellular concentration of Ca(2+) ([Ca(2+)](i)) (Ca(2+) transients) were also examined in fura-2-loaded preparations. KEY RESULTS Imatinib (1-10 microM) suppressed spontaneous contractions and Ca(2+) transients. Simultaneous recordings of electrical and mechanical activity demonstrated that imatinib (1 microM) reduced the amplitude of spontaneous contractions without suppressing corresponding slow waves. In the presence of nifedipine (1 microM), imatinib (10 microM) reduced the duration of slow waves and follower potentials in the antrum and accelerated their generation, but had little affect on their amplitude. In contrast, imatinib reduced the amplitude of antral slow potentials and slow waves in the corpus. CONCLUSIONS AND IMPLICATIONS Imatinib may suppress spontaneous contractions of gastric smooth muscles by inhibiting pathways that increase [Ca(2+)](i) in smooth muscles rather than by specifically inhibiting the activity of ICC. A high concentration of imatinib (10 microM) reduced the duration of slow waves or follower potentials in the antrum, which reflect activity of ICC distributed in the myenteric layers (ICC-MY), and suppressed antral slow potentials or corporal slow waves, which reflect activity of ICC within the muscle bundles (ICC-IM), presumably by inhibiting intracellular Ca(2+) handling.
Collapse
Affiliation(s)
- H Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
| | | | | |
Collapse
|
97
|
Kunisawa Y, Komuro T. Interstitial cells of Cajal associated with the submucosal plexus of the Guinea-pig stomach. Neurosci Lett 2008; 434:273-6. [PMID: 18329803 DOI: 10.1016/j.neulet.2008.01.063] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 01/18/2008] [Accepted: 01/19/2008] [Indexed: 10/22/2022]
Abstract
Interstitial cells of Cajal (ICC) form specialized networks in the gastrointestinal tract that coordinate cellular communications between nerves and smooth muscle cells. However, little is known about ICC in the gut mucosa or submucosa. Here, we report for the first time that Kit-immunoreactive ICC are associated with the submucosal (Meissner's) plexus of the Guinea-pig stomach. In longitudinal sections along the greater curvature of the gastric corpus, short spindle-shaped ICC of the submucosal plexus (ICC-SP) were located around the PGP9.5-immunoreactive nerve elements in the submucosa. Observations of whole-mount preparations clearly demonstrated Kit-immunoreactive bipolar or multipolar cells with long cytoplasmic processes about 100 microm in length. Such cells had typical characteristics of ICC, confirming that they were not mast cells, which are also Kit-immunoreactive residents of the submucosal connective tissue space. Although some ICC-SP surrounded parts of the submucosal plexus, they did not appear to form wide extensions of the cellular network, suggesting that they acted locally. The demonstration of ICC-SP in the submucosal connective tissue space suggests that they may contribute to the regulation of secretion, absorption and transportation of fluids in the mucosa.
Collapse
Affiliation(s)
- Yumi Kunisawa
- Laboratory of Histology and Neuroscience, Department of Health Science and Social Welfare, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama 359-1192, Japan
| | | |
Collapse
|
98
|
Abstract
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.
Collapse
Affiliation(s)
- Sushil K Sarna
- Enteric Neuromuscular Disorders and Visceral Pain Center, Division of Gastroenterology, Department of Internal Medicine, Neuroscience, and Cell Biology, The University of Texas Medical Branch at Gavelston, Galveston, TX 77555-1064, USA.
| |
Collapse
|
99
|
Nakayama S, Kajioka S, Goto K, Takaki M, Liu HN. Calcium-associated mechanisms in gut pacemaker activity. J Cell Mol Med 2008; 11:958-68. [PMID: 17979877 PMCID: PMC4401267 DOI: 10.1111/j.1582-4934.2007.00107.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
A considerable body of evidence has revealed that interstitial cells of Cajal (ICC), identified with c-Kit-immunoreactivity, act as gut pacemaker cells, with spontaneous Ca2+ activity in ICC as the probable primary mechanism. Namely, intracellular (cytosolic) Ca2+ oscillations in ICC periodically activate plasmalemmal Ca2+-dependent ion channels and thereby generate pacemaker potentials. This review will, thus, focus on Ca2+-associated mechanisms in ICC in the gastrointestinal (GI) tract, including auxiliary organs.
Collapse
Affiliation(s)
- Shinsuke Nakayama
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
| | | | | | | | | |
Collapse
|
100
|
Kim M, Hennig GW, Smith TK, Perrino BA. Phospholamban knockout increases CaM kinase II activity and intracellular Ca2+ wave activity and alters contractile responses of murine gastric antrum. Am J Physiol Cell Physiol 2007; 294:C432-41. [PMID: 18045856 DOI: 10.1152/ajpcell.00418.2007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phospholamban (PLB) inhibits the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA), and this inhibition is relieved by Ca(2+) calmodulin-dependent protein kinase II (CaM kinase II) phosphorylation. We previously reported significant differences in contractility, SR Ca(2+) release, and CaM kinase II activity in gastric fundus smooth muscles as a result of PLB phosphorylation by CaM kinase II. In this study, we used PLB-knockout (PLB-KO) mice to directly examine the effect of PLB absence on contractility, CaM kinase II activity, and intracellular Ca(2+) waves in gastric antrum smooth muscles. The frequencies and amplitudes of spontaneous phasic contractions were elevated in antrum smooth muscle strips from PLB-KO mice. Bethanecol increased the amplitudes of phasic contractions in antrum smooth muscles from both control and PLB-KO mice. Caffeine decreased and cyclopiazonic acid (CPA) increased the basal tone of antrum smooth muscle strips from PLB-KO mice, but the effects were less pronounced compared with control strips. The CaM kinase II inhibitor KN-93 was less effective at inhibiting caffeine-induced relaxation in antrum smooth muscle strips from PLB-KO mice. CaM kinase II autonomous activity was elevated, and not further increased by caffeine, in antrum smooth muscles from PLB-KO mice. Similarly, the intracellular Ca(2+) wave frequency was elevated, and not further increased by caffeine, in antrum smooth muscles from PLB-KO mice. These findings suggest that PLB is an important modulator of gastric antrum smooth muscle contractility by modulation of SR Ca(2+) release and CaM kinase II activity.
Collapse
Affiliation(s)
- Minkyung Kim
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | | | |
Collapse
|