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Athavale ON, Di Natale MR, Avci R, Clark AR, Furness JB, Cheng LK, Du P. Mapping the rat gastric slow-wave conduction pathway: bridging in vitro and in vivo methods, revealing a loosely coupled region in the distal stomach. Am J Physiol Gastrointest Liver Physiol 2024; 327:G254-G266. [PMID: 38860855 PMCID: PMC11427108 DOI: 10.1152/ajpgi.00069.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 06/04/2024] [Accepted: 06/10/2024] [Indexed: 06/12/2024]
Abstract
Rhythmic electrical events, termed slow waves, govern the timing and amplitude of phasic contractions of the gastric musculature. Extracellular multielectrode measurement of gastric slow waves can be a biomarker for phenotypes of motility dysfunction. However, a gastric slow-wave conduction pathway for the rat, a common animal model, is unestablished. In this study, the validity of extracellular recording was demonstrated in vitro with simultaneous intracellular and extracellular recordings and by pharmacological inhibition of slow waves. The conduction pathway was determined by in vivo extracellular recordings while considering the effect of motion. Slow-wave characteristics [means (SD)] varied regionally having higher amplitude in the antrum than the distal corpus [1.03 (0.12) mV vs. 0.75 (0.31) mV; n = 7; P = 0.025 paired t test] and faster propagation near the greater curvature than the lesser curvature [1.00 (0.14) mm·s-1 vs. 0.74 (0.14) mm·s-1; n = 9 GC, 7 LC; P = 0.003 unpaired t test]. Notably, in some subjects, separate wavefronts propagated near the lesser and greater curvatures with a loosely coupled region occurring in the area near the distal corpus midline at the interface of the two wavefronts. This region had either the greater or lesser curvature wavefront propagating through it in a time-varying manner. The conduction pattern suggests that slow waves in the rat stomach form annular wavefronts in the antrum and not the corpus. This study has implications for interpretation of the relationship between slow waves, the interstitial cells of Cajal network structure, smooth muscles, and gastric motility.NEW & NOTEWORTHY Mapping of rat gastric slow waves showed regional variations in their organization. In some subjects, separate wavefronts propagated near the lesser and greater curvatures with a loosely coupled region near the midline, between the wavefronts, having a varying slow-wave origin. Furthermore, simultaneous intracellular and extracellular recordings were concordant and independent of movement artifacts, indicating that extracellular recordings can be interpreted in terms of their intracellular counterparts when intracellular recording is not possible.
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Affiliation(s)
- Omkar N Athavale
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Madeleine R Di Natale
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy & Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Recep Avci
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Alys R Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Department of Anatomy & Physiology, University of Melbourne, Parkville, Victoria, Australia
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Cai W, Makwana R, Straface M, Gharibans A, Andrews PLR, Sanger GJ. Evidence for tetrodotoxin-resistant spontaneous myogenic contractions of mouse isolated stomach that are dependent on acetylcholine. Br J Pharmacol 2021; 179:1187-1200. [PMID: 34519057 PMCID: PMC9297954 DOI: 10.1111/bph.15685] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/03/2021] [Accepted: 09/06/2021] [Indexed: 12/24/2022] Open
Abstract
Background and Purpose Gastric pacemaker cells, interstitial cells of Cajal (ICC), are believed to initiate myogenic (non‐neuronal) contractions. These become damaged in gastroparesis, associated with dysrhythmic electrical activity and nausea. We utilised mouse isolated stomach to model myogenic contractions and investigate their origin and actions of interstitial cells of Cajal modulators. Experimental Approach Intraluminal pressure was recorded following distension with a physiological volume; tone, contraction amplitude and frequency were quantified. Compounds were bath applied. Key Results The stomach exhibited regular large amplitude contractions (median amplitude 9.0 [4.7–14.8] cmH2O, frequency 2.9 [2.5–3.4] c.p.m; n = 20), appearing to progress aborally. Tetrodotoxin (TTX, 10−6 M) had no effect on tone, frequency or amplitude but blocked responses to nerve stimulation. ω‐conotoxin GVIA (10−7 M) ± TTX was without effect on baseline motility. In the presence of TTX, (1) atropine (10−10–10−6 M) reduced contraction amplitude and frequency in a concentration‐related manner (pIC50 7.5 ± 0.3 M for amplitude), (2) CaCC channel (previously ANO1) inhibitors MONNA and CaCCinh‐A01 reduced contraction amplitude (significant at 10−5, 10−4 M respectively) and frequency (significant at 10−5 M), and (3), neostigmine (10−5 M) evoked a large, variable, increase in contraction amplitude, reduced by atropine (10−8–10−6 M) but unaffected (exploratory study) by the H1 receptor antagonist mepyramine (10−6 M). Conclusions and Implications The distended mouse stomach exhibited myogenic contractions, resistant to blockade of neural activity by TTX. In the presence of TTX, these contractions were prevented or reduced by compounds blocking interstitial cells of Cajal activity or by atropine and enhanced by neostigmine (antagonised by atropine), suggesting involvement of non‐neuronal ACh in their regulation.
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Affiliation(s)
- Weigang Cai
- Blizard Institute and the National Centre for Bowel Research, Barts The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Raj Makwana
- Blizard Institute and the National Centre for Bowel Research, Barts The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Marilisa Straface
- Blizard Institute and the National Centre for Bowel Research, Barts The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Armen Gharibans
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Paul L R Andrews
- Division of Biomedical Sciences, St George's University of London, London, UK
| | - Gareth J Sanger
- Blizard Institute and the National Centre for Bowel Research, Barts The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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Chen Q, Jiang Z, Zhang J, Cao L, Chen Z. Arecoline hydrobromide enhances jejunum smooth muscle contractility via voltage-dependent potassium channels in W/Wv mice. Physiol Res 2021; 70:437-446. [PMID: 33982580 DOI: 10.33549/physiolres.934557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Gastrointestinal motility was disturbed in W/Wv, which were lacking of interstitial cells of Cajal (ICC). In this study, we have investigated the role of arecoline hydrobromide (AH) on smooth muscle motility in the jejunum of W/Wv and wild-type (WT) mice. The jejunum tension was recorded by an isometric force transducer. Intracellular recording was used to identify whether AH affects slow wave and resting membrane potential (RMP) in vitro. The whole-cell patch clamp technique was used to explore the effects of AH on voltage-dependent potassium channels for jejunum smooth muscle cells. AH enhanced W/Wv and WT jejunum contractility in a dose-dependent manner. Atropine and nicardipine completely blocked the excitatory effect of AH in both W/Wv and WT. TEA did not reduce the effect of AH in WT, but was sufficient to block the excitatory effect of AH in W/Wv. AH significantly depolarized the RMP of jejunum cells in W/Wv and WT. After pretreatment with TEA, the RMP of jejunum cells indicated depolarization in W/Wv and WT, but subsequently perfused AH had no additional effect on RMP. AH inhibited the voltage-dependent K+ currents of acutely isolated mouse jejunum smooth muscle cells. Our study demonstrate that AH enhances the contraction activity of jejunum smooth muscle, an effect which is mediated by voltage-dependent potassium channels that acts to enhance the excitability of jejunum smooth muscle cells in mice.
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Affiliation(s)
- Q Chen
- Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China.
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de Sousa LN, Sant'ana DSP, Siqueira dos Santos RG, dos Santos Ribeiro AEA, da Costa CF, de Oliveira AP, Almeida JRGDS, Jucá DM, da Silva MTB, dos Santos AA, Palheta Junior RC. Involvement of serotonergic pathways in gastric dysmotility induced by fat burning nutritional supplements in mice. CURRENT RESEARCH IN PHARMACOLOGY AND DRUG DISCOVERY 2021; 2:100018. [PMID: 34909653 PMCID: PMC8663933 DOI: 10.1016/j.crphar.2021.100018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 01/20/2021] [Accepted: 02/01/2021] [Indexed: 11/30/2022] Open
Abstract
Fat burners are a category of nutritional supplements that are claimed to increase the metabolism and promote greater energy expenditure, leading to weight loss. However, little is known about the side effects on gastrointestinal motility. In this study, we evaluated the effect of ingestion with a fat burner named Thermbuterol® (THERM) on the gastric motility and food behavior of mice. THERM compounds were identified using nuclear magnetic resonance (NMR). Mice received variable doses of THERM (10, 50, 100 or 300 mg/kg, p.o.) or NaCl 0.15 M (control). Gastric emptying (GE) was assessed using the phenol red technique. Another set of mice was pretreated with intraperitoneal administration of hexamethonium (HEXA, 10 mg/kg), prazosin (PRAZ, 0.25 mg/kg), propranolol (PROP, 2 mg/kg), parachlorophenylalanine (PCPA, 300 mg/kg) or ondansetron (ONDA, 50 μg/kg) 30 min before THERM treatment for evaluation of GE. We assessed the gastrointestinal responsiveness in vitro as well as THERM's effects on food behavior. Caffeine was the major compound of THERM, identified by NMR. THERM 100 and 300 mg/kg decreased GE compared to the respective controls. Pretreatment with PRAZ or PROP did not prevent gastric dysmotility induced by THERM 100 mg/kg. However, the pretreatment with HEXA, ONDA or PCPA prevented GE delay induced by THERM. In vitro, THERM relaxed contractions in strips of longitudinal gastric fundus and duodenum. THERM also increased food intake, which was prevented by PCPA and ONDA treatments. THERM decreased GE of a liquid and increased food intake in mice, a phenomenon mediated by the autonomic nicotinic receptors and serotoninergic receptor.
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Affiliation(s)
| | | | | | | | - Camila F. da Costa
- Federal University of São Francisco Valley, Petrolina, Pernambuco, Brazil
| | | | | | - Davi M. Jucá
- Belo Horizonte University Center, Cristiano Machado Campus. Belo Horizonte, Minas Gerais, Brazil
| | - Moisés Tolentino Bento da Silva
- Laboratory of Exercise and Gastrointestinal Tract – Department of Physical Education, Federal University of Piauí, Teresina, Piauí, Brazil
| | - Armênio A. dos Santos
- Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Fortaleza, Ceará, Brazil
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Detection of gastric slow oscillatory contraction using parasagittal cine MR images: Comparison with simultaneously measured electrogastrogram. Magn Reson Imaging 2020; 75:149-155. [PMID: 33137456 DOI: 10.1016/j.mri.2020.10.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/24/2020] [Accepted: 10/26/2020] [Indexed: 11/22/2022]
Abstract
PURPOSE To determine if parasagittal gastric cine magnetic resonance imaging (MRI) is able to measure gastric oscillatory contractions around 0.05 Hz and to determine its relationship with electrical activity as measured by electrogastrography (EGG). METHODS Assessment of the gastric motility is important for the research of the enteric nervous system and for the diagnosis of functional gastric disorders. Electrogastrography is a non-invasive method that can measure gastric oscillatory electrical activity around 0.05 Hz (slow wave) using electrodes on the abdominal skin, but its sensitivity and specificity of the slow wave detection is limited. We used parasagittal gastric cine MRI around the angular incisure to measure gastric oscillatory contraction around 0.05 Hz in 24 healthy volunteers. Cine MRI was acquired with time resolution of 1 s for 10 min while freely breathing participants were lying on the bed. The gastric area of the cross section was measured for each MR image and assessed its change over time. The results were compared with those for simultaneously recorded EGG. RESULTS The main frequency of the gastric area change for each participant ranged from 0.041 to 0.059 Hz (mean ± S.D. = 0.049 ± 0.004), which corresponds to the gastric slow wave frequency (mean ± S.D. = 0.049 ± 0.004) as measured by EGG (p = 7.9585 × 10 -8, Kendall 's tau test). Cross correlation analysis showed that 22 of 24 participants' gastric area changes were significantly (p < 0.05) related to the EGG waveforms. Displacement of the stomach due to respiration did not affect gastric area measurements. CONCLUSIONS Parasagittal cine MRI is correlated with EGG recordings and able to detect and quantifying gastric motility abnormalities.
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Sanders KM. Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:3-46. [PMID: 31183821 PMCID: PMC7035145 DOI: 10.1007/978-981-13-5895-1_1] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The gastrointestinal (GI) tract has multifold tasks of ingesting, processing, and assimilating nutrients and disposing of wastes at appropriate times. These tasks are facilitated by several stereotypical motor patterns that build upon the intrinsic rhythmicity of the smooth muscles that generate phasic contractions in many regions of the gut. Phasic contractions result from a cyclical depolarization/repolarization cycle, known as electrical slow waves, which result from intrinsic pacemaker activity. Interstitial cells of Cajal (ICC) are electrically coupled to smooth muscle cells (SMCs) and generate and propagate pacemaker activity and slow waves. The mechanism of slow waves is dependent upon specialized conductances expressed by pacemaker ICC. The primary conductances responsible for slow waves in mice are Ano1, Ca2+-activated Cl- channels (CaCCs), and CaV3.2, T-type, voltage-dependent Ca2+ channels. Release of Ca2+ from intracellular stores in ICC appears to be the initiator of pacemaker depolarizations, activation of T-type current provides voltage-dependent Ca2+ entry into ICC, as slow waves propagate through ICC networks, and Ca2+-induced Ca2+ release and activation of Ano1 in ICC amplifies slow wave depolarizations. Slow waves conduct to coupled SMCs, and depolarization elicited by these events enhances the open-probability of L-type voltage-dependent Ca2+ channels, promotes Ca2+ entry, and initiates contraction. Phasic contractions timed by the occurrence of slow waves provide the basis for motility patterns such as gastric peristalsis and segmentation. This chapter discusses the properties of ICC and proposed mechanism of electrical rhythmicity in GI muscles.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA.
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Hashitani H, Mitsui R, Miwa-Nishimura K, Lam M. Role of capillary pericytes in the integration of spontaneous Ca 2+ transients in the suburothelial microvasculature in situ of the mouse bladder. J Physiol 2018; 596:3531-3552. [PMID: 29873405 DOI: 10.1113/jp275845] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/21/2018] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS In the bladder suburothelial microvasculature, pericytes in different microvascular segments develop spontaneous Ca2+ transients with or without associated constrictions. Spontaneous Ca2+ transients in pericytes of all microvascular segments primarily rely on the cycles of Ca2+ uptake and release by the sarco- and endoplasmic reticulum. The synchrony of spontaneous Ca2+ transients in capillary pericytes exclusively relies on the spread of depolarizations resulting from the opening of Ca2+ -activated chloride channels (CaCCs) via gap junctions. CaCC-dependent depolarizations further activate L-type voltage-dependent Ca2+ channels as required for the synchrony of Ca2+ transients in pericytes of pre-capillary arterioles, post-capillary venules and venules. Capillary pericytes may drive spontaneous Ca2+ transients in pericytes within the suburothelial microvascular network by sending CaCC-dependent depolarizations via gap junctions. ABSTRACT Mural cells in the microvasculature of visceral organs develop spontaneous Ca2+ transients. However, the mechanisms underlying the integration of these Ca2+ transients within a microvascular unit remain to be clarified. In the present study, the origin of spontaneous Ca2+ transients and their propagation in the bladder suburothelial microvasculature were explored. Cal-520 fluorescence Ca2+ imaging and immunohistochemistry were carried out on mural cells using mice expressing red fluorescent protein (DsRed) under control of the NG2 promotor. NG2(+) pericytes in both pre-capillary arterioles (PCAs) and capillaries developed synchronous spontaneous Ca2+ transients. By contrast, although NG2-DsRed also labelled arteriolar smooth muscle cells, these cells remained quiescent. Both NG2(+) pericytes in post-capillary venules (PCVs) and NG2(-) venular pericytes exhibited propagated Ca2+ transients. L-type voltage-dependent Ca2+ channel (LVDCC) blockade with nifedipine prevented Ca2+ transients or disrupted their synchrony in PCA, PCV and venular pericytes without dis-synchronizing Ca2+ transients in capillary pericytes. Blockade of gap junctions with carbenoxolone or Ca2+ -activated chloride channels (CaCCs) with 4,4'-diisothiocyanato-2,2'-stilbenedisulphonic acid disodium salt prevented Ca2+ transients in PCA and venular pericytes and disrupted the synchrony of Ca2+ transients in capillary and PCV pericytes. Spontaneous Ca2+ transients in pericytes of all microvascular segments were abolished or suppressed by cyclopiazonic acid, caffeine or tetracaine. The synchrony of Ca2+ transients in capillary pericytes arising from spontaneous Ca2+ release from the sarco- and endoplasmic reticulum appears to rely exclusively on CaCC activation, whereas subsequent LVDCC activation is required for the synchrony of Ca2+ transients in pericytes of other microvascular segments. Capillary pericytes may drive spontaneous activity in the suburothelial microvascular unit to facilitate capillary perfusion.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Retsu Mitsui
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Kyoko Miwa-Nishimura
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Michelle Lam
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
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Sevgili AM, Balkanci DZ, Erdem A. Potential excitatory role of nitric oxide on 2-deoxy- d-glucose-induced gastric motility in rats. Clin Exp Pharmacol Physiol 2017; 44:693-699. [DOI: 10.1111/1440-1681.12749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 02/28/2017] [Accepted: 03/03/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Ayse M. Sevgili
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
| | - Dicle Z. Balkanci
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
| | - Aysen Erdem
- Department of Pharmacology; Faculty of Medicine; Hacettepe University, Sıhhiye; Ankara Turkey
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Lentle RG, Reynolds GW, Hulls CM, Chambers JP. Advanced spatiotemporal mapping methods give new insights into the coordination of contractile activity in the stomach of the rat. Am J Physiol Gastrointest Liver Physiol 2016; 311:G1064-G1075. [PMID: 27765760 DOI: 10.1152/ajpgi.00308.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/12/2016] [Indexed: 01/31/2023]
Abstract
We used spatiotemporal mapping of strain rate to determine the direction of propagation and amplitudes of the longitudinal and circumferential components of antrocorporal (AC) contractions and fundal contractions in the rat stomach maintained ex vivo and containing a volume of fluid that was within its normal functional capacity. In the region of the greater curvature the longitudinal and circular components of AC contractions propagated synchronously at right angles to the arciform geometric axis of the stomach. However, the configuration of AC contractions was U shaped, neither the circular nor the longitudinal component of contractions being evident in the upper proximal corpus. Similarly, in the distal upper antrum of some preparations, circumferential components propagated more rapidly than longitudinal components. Ongoing "high-frequency, low-amplitude myogenic contractions" were identified in the upper proximal gastric corpus and on the anterior and posterior wall of the fundus. The amplitudes of these contractions were modulated in the occluded stomach by low-frequency pressure waves that occurred spontaneously. Hence the characteristics of phasic contractions vary regionally in the antrum and corpus and a previously undescribed high-frequency contractile component was identified in the proximal corpus and fundus, the latter being modulated in synchrony with cyclic variation in intrafundal pressure in the occluded fundus.
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Affiliation(s)
- R G Lentle
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - G W Reynolds
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - C M Hulls
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - J P Chambers
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Calabresi MFF, Quini CC, Matos JF, Moretto GM, Americo MF, Graça JRV, Santos AA, Oliveira RB, Pina DR, Miranda JRA. Alternate current biosusceptometry for the assessment of gastric motility after proximal gastrectomy in rats: a feasibility study. Neurogastroenterol Motil 2015; 27:1613-20. [PMID: 26303680 DOI: 10.1111/nmo.12660] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 07/25/2015] [Indexed: 12/12/2022]
Abstract
BACKGROUND This study proposes an experimental model to assess the consequences of gastric surgeries on gastric motility. We investigated the effects of proximal gastrectomy (PG) using a non-invasive technique (alternate current biosusceptometry [ACB]) on gastric contractility (GC), gastric emptying (GE), and orocecal transit (OCT) after the ingestion of liquids and solids in rats. METHODS Twenty-four male rats were subjected to gastric motility assessment before and after the PG procedure. The GE and OCT results are expressed as the mean time of gastric emptying (MGET) and cecum arrival (MCAT). The GC recordings are presented as the frequency and amplitude of contractions. KEY RESULTS Mean time of gastric emptying after solid meals were significantly different (p < 0.001) between control and PG (113 ± 5 to 99 ± 6 min). Mean time of cecum arrival ranged from 265 ± 9 to 223 ± 11 min (p < 0.001) and 164 ± 9 to 136 ± 17 min (p < 0.050) for solid and liquid meals, respectively. The assessment of GC showed that surgery decreased the phasic frequency (4.4 ± 0.4 to 3.0 ± 1.1 cpm, p < 0.050) and increased the amplitude of contractions (3.6 ± 2.7 to 7.2 ± 3.0 V/s, p < 0.050). No significant difference was found in tonic frequency. CONCLUSIONS & INFERENCES The ACB system was able to assess GE, OCT, and GC in gastrectomized rats. Overall, PG accelerated GE and gastrointestinal transit, likely due to the increase in both intragastric pressure and amplitude contraction. Our data presented an efficient model to investigate functional consequences from gastric surgeries that will allow further studies involving different procedures.
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Affiliation(s)
- M F F Calabresi
- Departamento de Física e Biofísica, Instituto de Biociências de Botucatu, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
| | - C C Quini
- Departamento de Física e Biofísica, Instituto de Biociências de Botucatu, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
| | - J F Matos
- Departamento de Física e Biofísica, Instituto de Biociências de Botucatu, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
| | - G M Moretto
- Departamento de Física e Biofísica, Instituto de Biociências de Botucatu, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
| | - M F Americo
- Instituto de Ciências Biológicas e da Saúde, UFMT-Universidade Federal de Mato Grosso, Barra do Garças, Mato Grosso, Brazil
| | - J R V Graça
- Departamento de Fisiologia, Faculdade de Medicina de Sobral, UFC-Universidade Federal do Ceará, Sobral, Ceará, Brazil
| | - A A Santos
- Departamento de Fisiologia e Farmacologia, Faculdade de Medicina, UFC-Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - R B Oliveira
- Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, USP-Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - D R Pina
- Departamento de Doenças Tropicais e Diagnóstico por Imagem, Faculdade de Medicina de Botucatu, UNESP - Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
| | - J R A Miranda
- Departamento de Física e Biofísica, Instituto de Biociências de Botucatu, UNESP-Universidade Estadual Paulista, Botucatu, São Paulo, Brazil
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Blair PJ, Rhee PL, Sanders KM, Ward SM. The significance of interstitial cells in neurogastroenterology. J Neurogastroenterol Motil 2014; 20:294-317. [PMID: 24948131 PMCID: PMC4102150 DOI: 10.5056/jnm14060] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 06/06/2014] [Accepted: 06/07/2014] [Indexed: 12/21/2022] Open
Abstract
Smooth muscle layers of the gastrointestinal tract consist of a heterogeneous population of cells that include enteric neurons, several classes of interstitial cells of mesenchymal origin, a variety of immune cells and smooth muscle cells (SMCs). Over the last number of years the complexity of the interactions between these cell types has begun to emerge. For example, interstitial cells, consisting of both interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor alpha-positive (PDGFRα(+)) cells generate pacemaker activity throughout the gastrointestinal (GI) tract and also transduce enteric motor nerve signals and mechanosensitivity to adjacent SMCs. ICC and PDGFRα(+) cells are electrically coupled to SMCs possibly via gap junctions forming a multicellular functional syncytium termed the SIP syncytium. Cells that make up the SIP syncytium are highly specialized containing unique receptors, ion channels and intracellular signaling pathways that regulate the excitability of GI muscles. The unique role of these cells in coordinating GI motility is evident by the altered motility patterns in animal models where interstitial cell networks are disrupted. Although considerable advances have been made in recent years on our understanding of the roles of these cells within the SIP syncytium, the full physiological functions of these cells and the consequences of their disruption in GI muscles have not been clearly defined. This review gives a synopsis of the history of interstitial cell discovery and highlights recent advances in structural, molecular expression and functional roles of these cells in the GI tract.
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Affiliation(s)
- Peter J Blair
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
| | - Poong-Lyul Rhee
- Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
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Blair PJ, Rhee PL, Sanders KM, Ward SM. The significance of interstitial cells in neurogastroenterology. J Neurogastroenterol Motil 2014. [PMID: 24948131 DOI: 10.5056/jnm140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Smooth muscle layers of the gastrointestinal tract consist of a heterogeneous population of cells that include enteric neurons, several classes of interstitial cells of mesenchymal origin, a variety of immune cells and smooth muscle cells (SMCs). Over the last number of years the complexity of the interactions between these cell types has begun to emerge. For example, interstitial cells, consisting of both interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor alpha-positive (PDGFRα(+)) cells generate pacemaker activity throughout the gastrointestinal (GI) tract and also transduce enteric motor nerve signals and mechanosensitivity to adjacent SMCs. ICC and PDGFRα(+) cells are electrically coupled to SMCs possibly via gap junctions forming a multicellular functional syncytium termed the SIP syncytium. Cells that make up the SIP syncytium are highly specialized containing unique receptors, ion channels and intracellular signaling pathways that regulate the excitability of GI muscles. The unique role of these cells in coordinating GI motility is evident by the altered motility patterns in animal models where interstitial cell networks are disrupted. Although considerable advances have been made in recent years on our understanding of the roles of these cells within the SIP syncytium, the full physiological functions of these cells and the consequences of their disruption in GI muscles have not been clearly defined. This review gives a synopsis of the history of interstitial cell discovery and highlights recent advances in structural, molecular expression and functional roles of these cells in the GI tract.
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Affiliation(s)
- Peter J Blair
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Poong-Lyul Rhee
- Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kenton M Sanders
- 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
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Abstract
Gastrointestinal (GI) motility function and its regulation is a complex process involving collaboration and communication of multiple cell types such as enteric neurons, interstitial cells of Cajal (ICC), and smooth muscle cells. Recent advances in GI research made a better understanding of ICC function and their role in the GI tract, and studies based on different types of techniques have shown that ICC, as an integral part of the GI neuromuscular apparatus, transduce inputs from enteric motor neurons, generate intrinsic electrical rhythmicity in phasic smooth muscles, and have a mechanical sensation ability. Absence or improper function of these cells has been linked to some GI tract disorders. This paper provides a general overview of ICC; their discovery, subtypes, function, locations in the GI tract, and some disorders associated with their loss or disease, and highlights some controversial issues with regard to the importance of ICC in the GI tract.
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Affiliation(s)
- Othman A. Al-Shboul
- Department of Physiology, Jordan University of Science and Technology, Irbid, Jordan,Address for correspondence: Dr. Othman Abdullah Al-Shboul, Department of Physiology, Jordan University of Science and Technology, P.O. Box 3030, Irbid - 22110, Jordan. E-mail:
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14
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Zurr L, Leonhard-Marek S. Effects of β-hydroxybutyrate and different calcium and potassium concentrations on the membrane potential and motility of abomasal smooth muscle cells in cattle. J Dairy Sci 2012; 95:5750-9. [PMID: 22921615 DOI: 10.3168/jds.2012-5479] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 06/25/2012] [Indexed: 11/19/2022]
Affiliation(s)
- L Zurr
- Department of Physiology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15, 30173 Hannover, Germany
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15
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Kito Y. The functional role of intramuscular interstitial cells of Cajal in the stomach. J Smooth Muscle Res 2011; 47:47-53. [PMID: 21757854 DOI: 10.1540/jsmr.47.47] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Intramuscular interstitial cells of Cajal (ICC-IM) are found within the smooth muscle layers of the stomach. ICC-IM are mainly spindle shaped cells with bipolar processes orientated along the long axis of surrounding smooth muscle cells. ICC-IM make close contacts with nerve varicosities and form gap junctions with neighbouring smooth muscle cells, indicating that ICC-IM mediate enteric motor neurotransmission. These morphological properties of ICC-IM are similar throughout the stomach. However, the electrical properties of these cells differ from region to region. In the fundus, ICC-IM generate spontaneous transient depolarizations (STDs), resulting in an ongoing discharge of unitary potentials in the smooth muscle cells. ICC-IM in the corpus generate slow waves and as they fire at the highest frequency they serve as the dominant pacemaker cells in the stomach. On the other hand, ICC-IM in the antrum generate the secondary component of slow waves triggered by the initial component that propagates passively from myenteric ICC (ICC-MY). Thus, the different electrical properties of ICC-IM play a critical role in creating the distinct functions of the proximal and distal regions of the stomach such that the fundus acts as a reservoir of food, the corpus as a dominant pacemaker region, while the antrum acts as a region for mixing and propulsion of food.
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Affiliation(s)
- Yoshihiko Kito
- Department of Physiology, Nagoya City University Medical School, Japan.
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16
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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.
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Affiliation(s)
- Yuhsuke Shigemasa
- Department of Cell Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya, Japan
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17
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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.
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Affiliation(s)
- Cheng-Zhong You
- Department of General Surgery, Zhong-Da Hospital, and Department of Physiology, Southeast University School of Medicine, 210009, Nanjing, China
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18
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Quantification of the effects of the volume and viscosity of gastric contents on antral and fundic activity in the rat stomach maintained ex vivo. Dig Dis Sci 2010; 55:3349-60. [PMID: 20198425 DOI: 10.1007/s10620-010-1164-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2009] [Accepted: 02/11/2010] [Indexed: 12/13/2022]
Abstract
AIMS The aim of this study was to examine the effect of varying the rheological properties of perfusate on the volume and muscular activity of the various compartments of the rat stomach. METHODS Image analysis was used to quantify the activity of the ex vivo stomach preparations when perfused according to a ramp profile. RESULTS The area of the fundus increased to a greater extent than that of the body when watery or viscous material was perfused. However, initial distension of the corpus was greater and occurred more rapidly when viscous material was perfused. Only the fundus expanded when perfusion followed the administration of verapamil. The frequency of antrocorporal contractions decreased significantly and the amplitude of antrocorporal contractions increased significantly with increase in gastric volume. The velocity of antrocorporal contractions did not vary with gastric volume but varied regionally in some preparations being faster distally than proximally. Neither the frequency, amplitude or velocity of antrocorporal contractions differed when pseudoplastic rather than watery fluid was perfused. However, the characteristics of antrocorporal contractions changed significantly when the stomach was perfused with material with rheological characteristics that induce different patterns of wall tension to those normally encountered. Hence, the mean frequency and speed of propagation of antrocorporal contractions increased and their direction of propagation became inconstant.
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19
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Buist ML, Corrias A, Poh YC. A model of slow wave propagation and entrainment along the stomach. Ann Biomed Eng 2010; 38:3022-30. [PMID: 20437204 DOI: 10.1007/s10439-010-0051-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 04/20/2010] [Indexed: 10/19/2022]
Abstract
Interstitial cells of Cajal (ICC) isolated from different regions of the stomach generate spontaneous electrical slow wave activity at different frequencies, with cells from the proximal stomach pacing faster than their distal counterparts. However, in vivo there exists a uniform pacing frequency; slow waves propagate aborally from the proximal stomach and subsequently entrain distal tissues. Significant resting membrane potential (RMP) gradients also exist within the stomach whereby membrane polarization generally increases from the fundus to the antrum. Both of these factors play a major role in the macroscopic electrical behavior of the stomach and as such, any tissue or organ level model of gastric electrophysiology should ensure that these phenomena are properly described. This study details a dual-cable model of gastric electrical activity that incorporates biophysically detailed single-cell models of the two predominant cell types, the ICC and smooth muscle cells. Mechanisms for the entrainment of the intrinsic pacing frequency gradient and for the establishment of the RMP gradient are presented. The resulting construct is able to reproduce experimentally recorded slow wave activity and provides a platform on which our understanding of gastric electrical activity can advance.
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20
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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.
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Affiliation(s)
- Dirk F van Helden
- School of Biomedical Sciences, Faculty of Health, University of Newcastle, Callaghan, New South Wales, Australia.
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21
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Mishima Y, Amano Y, Takahashi Y, Mishima Y, Moriyama N, Miyake T, Ishimura N, Ishihara S, Kinoshita Y. Gastric emptying of liquid and solid meals at various temperatures: effect of meal temperature for gastric emptying. J Gastroenterol 2009; 44:412-8. [PMID: 19308311 DOI: 10.1007/s00535-009-0022-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 12/06/2008] [Indexed: 02/04/2023]
Abstract
BACKGROUND Patients with functional dyspepsia frequently show delayed gastric emptying, and dietary advice is frequently given for its improvement. If meal temperature influences gastric emptying, advice regarding the meal temperature may become a possible component of dietary therapy. However, little information exists concerning the thermal effect of meals on gastric emptying. The aim of this study was to determine the thermal effect of liquid and solid meals on gastric emptying. METHODS The gastric emptying of liquid and solid test meals was examined in healthy volunteers (liquid, n = 25, mean age = 35.7 +/- 9.6 years, male-to-female ratio = 22:3; solid, n = 25, mean age = 35.2 +/- 8.8 years, male-to-female ratio = 20:5). Gastric emptying after the ingestion of liquid or solid meals at three different temperatures (4, 37, and 60 degrees C) was investigated with the [(13)C]-labeled acetate breath test. The lag phase time (T (max-calc)) and the half-emptying time (T (1/2)) were calculated from the (13)CO(2) breath excretion curve as indices of gastric emptying. RESULTS The values of T (max-calc) at 60 degrees C with both the liquid and solid meals were significantly smaller than those at 37 degrees C (P < 0.05). However, there was no difference in the T (1/2) values. In the analysis of the percent excretion of (13)CO(2) in 1 h (% dose/h) data with the liquid meal test in the earlier phase within 30 min, significantly larger values were found at 60 degrees C than at the other temperatures. These findings suggest that a hot meal significantly accelerates gastric emptying. CONCLUSIONS Meal temperature may be considered as a component of dietary therapy for patients with functional dyspepsia.
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Affiliation(s)
- Yuko Mishima
- Department of Gastroenterology and Hepatology, School of Medicine, Shimane University, Izumo, Japan
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22
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Garcia-Lopez P, Garcia-Marin V, Martínez-Murillo R, Freire M. Updating old ideas and recent advances regarding the Interstitial Cells of Cajal. ACTA ACUST UNITED AC 2009; 61:154-69. [PMID: 19520112 DOI: 10.1016/j.brainresrev.2009.06.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2009] [Revised: 05/30/2009] [Accepted: 06/01/2009] [Indexed: 12/11/2022]
Abstract
Since their discovery by Cajal in 1889, the Interstitial Cells of Cajal (ICC) have generated much controversy in the scientific community. Indeed, the nervous, muscle or fibroblastic nature of the ICC has remained under debate for more than a century, as has their possible physiological function. Cajal and his colleagues considered them to be neurons, while contemporary histologists like Kölliker and Dogiel categorized these cells as fibroblasts. More recently, the role of ICC in the origin of slow-wave peristaltism has been elucidated, and several studies have shown that they participate in neurotransmission (intercalation theory). The fact that ICC assemble in the circular muscular layer and that they originate from cells which emerge from the ventral neural tube (VENT cells), a source of neurons, glia and ICC precursors other than the neural crest, suggests a neural origin for this particular subset of ICC. The discovery that ICC express the Kit protein, a type III tyrosine kinase receptor encoded by the proto-oncogene c-kit, has helped better understand their physiological role and implication in pathological conditions. Gleevec, a novel molecule designed to inhibit the mutant activated version of c-Kit receptors, is the drug of choice to treat the so-called gastrointestinal stromal tumours (GIST), the most common non-epithelial neoplasm of the gastrointestinal tract. Here we review Cajal's original contributions with the aid of unique images taken from Cajal's histological slides (preserved at the Cajal Museum, Cajal Institute, CSIC). In addition, we present a historical review of the concepts associated with this particular cell type, emphasizing current data that has advanced our understanding of the role these intriguing cells fulfil.
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Affiliation(s)
- P Garcia-Lopez
- Cajal Institute, CSIC, Avda Doctor Arce 37, 28002 - Madrid, Spain
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23
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Lammers WJEP, Ver Donck L, Stephen B, Smets D, Schuurkes JAJ. Origin and propagation of the slow wave in the canine stomach: the outlines of a gastric conduction system. Am J Physiol Gastrointest Liver Physiol 2009; 296:G1200-10. [PMID: 19359425 DOI: 10.1152/ajpgi.90581.2008] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Slow waves are known to originate orally in the stomach and to propagate toward the antrum, but the exact location of the pacemaker and the precise pattern of propagation have not yet been studied. Using assemblies of 240 extracellular electrodes, simultaneous recordings of electrical activity were made on the fundus, corpus, and antrum in open abdominal anesthetized dogs. The signals were analyzed off-line, pathways of slow wave propagation were reconstructed, and slow wave velocities and amplitudes were measured. The gastric pacemaker is located in the upper part of the fundus, along the greater curvature. Extracellularly recorded slow waves in the pacemaker area exhibited large amplitudes (1.8 +/- 1.0 mV) and rapid velocities (1.5 +/- 0.9 cm/s), whereas propagation in the remainder of the fundus and in the corpus was slow (0.5 +/- 0.2 cm/s) with low-amplitude waveforms (0.8 +/- 0.5 mV). In the antrum, slow wave propagation was fast (1.5 +/- 0.6 cm/s) with large amplitude deflections (2.0 +/- 1.3 mV). Two areas were identified where slow waves did not propagate, the first in the oral medial fundus and the second distal in the antrum. Finally, recordings from the entire ventral surface revealed the presence of three to five simultaneously propagating slow waves. High resolution mapping of the origin and propagation of the slow wave in the canine stomach revealed areas of high amplitude and rapid velocity, areas with fractionated low amplitude and low velocity, and areas with no propagation; all these components together constitute the elements of a gastric conduction system.
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Affiliation(s)
- Wim J E P Lammers
- Dept. of Physiology, Faculty of Medicine and Health Sciences, P.O.Box 17666, Al Ain, United Arab Emirates University, United Arab Emirates.
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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.
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Affiliation(s)
- Kazumasa Domae
- Department of Physiology, Nagoya City University Medical School, Japan
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25
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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
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26
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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.
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Affiliation(s)
- G D S Hirst
- Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan
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27
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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.
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Affiliation(s)
- H Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan.
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Abstract
There has been considerable speculation about the function of interstitial cells of Cajal (ICC) since their discovery more than 100 years ago. It has been difficult to study these cells under native conditions, but great insights about the function of ICC have come from studies of genetic models with loss-of function mutations in the Kit signalling pathway. First it was discovered that signalling via Kit (a receptor tyrosine kinase) was vital for the development and maintenance of the ICC phenotype in gastrointestinal (GI) muscles. In compound heterozygotes (W/W(V) and Sl/Sl(d) animals), where there are partial loss-of-function mutations in Kit receptors or Kit ligand (stem cell factor), ICC failed to develop in various regions of the GI tract, but no major changes in the smooth muscle layers or enteric nervous system occurred in the absence of these cells. Animals with these mutations provided an unprecedented opportunity to understand the role of ICC in GI motor function, and it is now clear from these studies that ICC serve as: (i) pacemaker cells, generating the spontaneous electrical rhythms of the gut known as slow waves; (ii) a propagation pathway for slow waves so that large areas of the musculature can be entrained to a dominant pacemaker frequency; (iii) mediators of excitatory cholinergic and inhibitory nitrergic neural inputs from the enteric nervous system, and (iv) stretch receptors that modulate membrane potential and electrical slow wave frequency. This review describes the use of genetic models to understand the important physiological role of ICC in the GI tract.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Nakayama S, Shimono K, Liu HN, Jiko H, Katayama N, Tomita T, Goto K. Pacemaker phase shift in the absence of neural activity in guinea-pig stomach: a microelectrode array study. J Physiol 2006; 576:727-38. [PMID: 16990400 PMCID: PMC1890421 DOI: 10.1113/jphysiol.2006.118893] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Gastrointestinal (GI) motility is well organized. GI muscles act as a functional syncytium to achieve physiological functions under the control of neurones and pacemaker cells, which generate basal spontaneous pacemaker electrical activity. To date, it is unclear how spontaneous electrical activities are coupled, especially within a micrometre range. Here, using a microelectrode array, we show a spatio-temporal analysis of GI spontaneous electrical activity. The muscle preparations were isolated from guinea-pig stomach, and fixed in a chamber with an array of 8 x 8 planar multielectrodes (with 300 microm in interpolar distance). The electrical activities (field potentials) were simultaneously recorded through a multichannel amplifier system after high-pass filtering at 0.1 Hz. Dihydropyridine Ca(2+) channel antagonists are known to differentiate the electrical pacemaker activity of interstitial cells of Cajal (ICCs) by suppressing smooth muscle activity. In the presence of nifedipine, we observed spontaneous electrical activities that were well synchronized over the array area, but had a clear phase shift depending on the distance. The additional application of tetrodotoxin (TTX) had little effect on the properties of the electrical activity. Furthermore, by constructing field potential images, we visualized the synchronization of pacemaker electrical activities resolving phase shifts that were measurable over several hundred micrometres. The results imply a phase modulation mechanism other than neural activity, and we postulate that this mechanism enables smooth GI motility. In addition, some preparations clearly showed plasticity of the pacemaker phase shift.
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Affiliation(s)
- Shinsuke Nakayama
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, 65 Tsuruma-cho, Showa-ku, Nagoya 466-8550, Japan.
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Suzuki H, Kito Y, Hashitani H, Nakamura E. Factors modifying the frequency of spontaneous activity in gastric muscle. J Physiol 2006; 576:667-74. [PMID: 16945968 PMCID: PMC1890408 DOI: 10.1113/jphysiol.2006.117093] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The cellular mechanisms that determine the frequency of spontaneous activity were investigated in gastric smooth muscles isolated from the guinea-pig. Intact antral muscle generated slow waves periodically; the interval between slow waves was decreased exponentially by depolarization of the membrane to reach a steady interval value of about 7 s. Isolated circular muscle bundles produced slow potentials spontaneously or were evoked by depolarizing current stimuli. Evoked slow potentials appeared in an all-or-none fashion, with a refractory period of approximately 2-3 s. Low concentrations of chemicals that modify intracellular signalling revealed that the refractory period was causally related to the activity of protein kinase C (PKC). Activation of PKC increased and inhibition of PKC activity decreased the frequency of slow potentials. Chemicals that inhibit mitochondrial functions reduced the frequency of slow waves. Inhibition of internal Ca(2+)-store activity decreased the amplitude, but not the frequency of slow potentials, suggesting that the amplitude is causally related to Ca(2+) release from the internal store. The results suggest that changes in [Ca(2+)](i) caused by the activity of mitochondria may play a key role in determining the frequency of spontaneous activity in gastric pacemaker cells.
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Affiliation(s)
- H Suzuki
- Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan.
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31
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Chen H, Redelman D, Ro S, Ward SM, Ordög T, Sanders KM. Selective labeling and isolation of functional classes of interstitial cells of Cajal of human and murine small intestine. Am J Physiol Cell Physiol 2006; 292:C497-507. [PMID: 16943245 DOI: 10.1152/ajpcell.00147.2006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Specific functions of interstitial cells of Cajal (ICC) have been linked to distinct classes that differ by morphology and distribution. In the small intestine, slow wave-generating ICC are located in the myenteric region (ICC-MY), whereas ICC that mediate neuromuscular neurotransmission occur either throughout the circular muscle layer (intramuscular ICC, ICC-IM) or in association with the deep muscular plexus (ICC-DMP). Selective isolation of ICC to characterize specific properties has been difficult. Recently, neurokinin-1 receptors have been detected in murine ICC-DMP and neurons but not in ICC-MY. Here we identified and isolated ICC-DMP/IM by receptor-mediated internalization of fluorescent substance P and Kit immunofluorescence. Specificity of labeling was verified by confocal microscopy. Mouse and human ICC-DMP/IM were detected in suspension by fluorescent microscopy and harvested for RT-PCR with micropipettes. The isolated cells expressed Kit but not markers for neurons, smooth muscle, or antigen-presenting cells. ICC-DMP expressed neurokinin-1 receptor, M(2) and M(3) muscarinic receptors, P2Y(1) and P2Y(4) purinergic receptors, VIP receptor 2, soluble guanylate cyclase-1 subunits, and protein kinase G. L- or T-type Ca(2+) channels were not detected in these cells. ICC-MY and ICC-DMP were simultaneously detected and enumerated by flow cytometry and sorted to purity by fluorescence-activated cell sorting. In summary, functional classes of ICC have distinct molecular identities that can be used to selectively identify and harvest these cells with, for example, receptor-mediated uptake of substance P and Kit immunofluorescence. ICC-DMP express neurotransmitter receptors and signaling intermediate molecules that are consistent with their role in neuromuscular neurotransmission.
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MESH Headings
- Animals
- Cell Separation
- Cells/classification
- Flow Cytometry
- Fluorescent Antibody Technique
- Humans
- Intestine, Small/cytology
- Intestine, Small/metabolism
- Intestine, Small/physiology
- Mice/anatomy & histology
- Mice, Inbred BALB C
- Microscopy, Confocal
- Microscopy, Fluorescence
- Muscle, Smooth/cytology
- Muscle, Smooth/metabolism
- Muscle, Smooth/physiology
- Proto-Oncogene Proteins c-kit/metabolism
- Receptors, Neurokinin-1/metabolism
- Receptors, Neurotransmitter/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Substance P/metabolism
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Affiliation(s)
- Hui Chen
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada-Reno, Reno, NV 89557, USA
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32
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Hirst GDS, Edwards FR. Electrical events underlying organized myogenic contractions of the guinea pig stomach. J Physiol 2006; 576:659-65. [PMID: 16873400 PMCID: PMC1890413 DOI: 10.1113/jphysiol.2006.116491] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The stomach generates a characteristic pattern of coordinated activity whereby rings of contraction regularly start in the corpus and migrate slowly down the stomach to the duodenum. This behaviour persists after isolating the stomach and after blocking nervous activity; hence the response is myogenic, resulting from organized contractions of smooth muscle cells lying in the stomach wall. Each ring of contraction is triggered by a long lasting wave of depolarization, termed a slow wave. Slow waves are now known to be generated by sets of interstitial cells of Cajal (ICC), which intermingle with gastric smooth muscle cells. This article describes some studies which identify the roles played by ICC in the on-going generation of coordinated gastric movements. Intramuscular ICC in the corpus generate slow waves and these provide the dominant pacemaker frequency in the stomach. Corporal slow waves, in turn, activate a network of myenteric ICC, which starts in the antrum and slowly conducts waves of depolarization down the stomach. As these waves pass over bundles of circularly orientated muscle cells, they activate a set of intramuscular ICC which lie in the circular muscle layer: these generate slow waves that rapidly spread radially, so triggering each ring of contraction.
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Affiliation(s)
- G David S Hirst
- Division of Neuroscience, John Curtin School of Medical Research, Canberra, ACT, 0200, Australia.
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33
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Affiliation(s)
- Marcello Costa
- Department of Physiology and Centre of Neuroscience, School of Medicine, Flinders University, Adelaide, SA, Australia.
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34
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Edwards FR, Hirst GDS. An electrical analysis of slow wave propagation in the guinea-pig gastric antrum. J Physiol 2005; 571:179-89. [PMID: 16357016 PMCID: PMC1805640 DOI: 10.1113/jphysiol.2005.100743] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
This paper provides an electrical description of the propagation of slow waves and pacemaker potentials in the guinea-pig gastric antrum in anal and circumferential directions. As electrical conduction between laterally adjacent circular muscle bundles is regularly interrupted, anal conduction of pacemaker potentials was assumed to occur via an electrically interconnected chain of myenteric interstitial cells of Cajal (ICC(MY)). ICC(MY) were also connected resistively to serially connected compartments of longitudinal muscle. Circumferential conduction occurred in a circular smooth muscle bundle that was represented as a chain of electrically connected isopotential compartments: each compartment contained a proportion of intramuscular interstitial cells of Cajal (ICC(IM)) that are responsible for the regenerative component of the slow wave. The circular muscle layer, which contains ICC(IM), and the ICC(MY) network incorporated a mechanism, modelled as a two-stage chemical reaction, which produces an intracellular messenger. The first stage of the reaction is proposed to be activated in a voltage-dependent manner as described by Hodgkin and Huxley; the messenger altered the mean rate of discharge of depolarizing unitary potentials as a function of the concentration of messenger according to a conventional dose-effect relationship. A separate membrane conductance, scaled by the product of an independent voltage-sensitive reaction, was included in the ICC(MY) compartments; this was used to describe the primary component of pacemaker potentials and simulated a delay before the activation of this membrane current. The model generates pacemaker potentials and slow waves with propagation velocities similar to those determined in the physiological experiments described in the accompanying paper.
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Affiliation(s)
- Frank R Edwards
- Division of Neuroscience, John Curtin School of Medical Research, Canberra, ACT, 0200, Australia.
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Hirst GDS, Garcia-Londoño AP, Edwards FR. Propagation of slow waves in the guinea-pig gastric antrum. J Physiol 2005; 571:165-77. [PMID: 16357017 PMCID: PMC1805648 DOI: 10.1113/jphysiol.2005.100735] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Intracellular recordings were made from the circular layer of the intact muscular wall of the guinea-pig gastric antrum in preparations where much of the corpus remained attached. When two electrodes were positioned parallel to and near to the greater curvature, slow waves were first detected at the oral site and subsequently at the anal site: the oro-anal conduction velocity was found to be 2.5 mm s(-1). When one electrode was positioned near the greater curvature and the other at a circumferential location, slow waves were first detected near the greater curvature and subsequently at the circumferential site: the circumferential conduction velocity was 13.9 mm s(-1). When recordings were made from preparations in which the circular muscle layer had been removed, the oro-anal and the circumferential conduction velocities were both about 3.5 mm s(-1). When slow waves were recorded from preparations in which much of the myenteric network of antral interstitial cells (ICC(MY)) had been dissected away, slow waves were first detected near the region of intact ICC(MY) and subsequently at a circumferential location: the circumferential conduction velocity of slow waves in regions devoid of ICC(MY) was 14.7 mm s(-1). When the electrical properties of isolated single bundles of circular muscle were determined, their length constants were about 3 mm and their time constant about 230 ms, giving an asymptotic electrotonic propagation velocity of 25 mm s(-1). Oro-anal electrical coupling between adjacent bundles of circular muscle was found to vary widely: some bundles were well connected to neighbouring bundles whereas others were not. Together the observations suggest that the slow oro-anal progression of slow waves results from a slow conduction velocity of pacemaker potentials in the myenteric network of interstitial cells. The rapid circumferential conduction of slow waves results from the electrical properties of the circular muscle layer which allow intramuscular ICC (ICC(IM)) to support the radial spread of slow waves: regions of high resistance between bundles prevent the anally directed spread of slow waves within the circular layer.
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Affiliation(s)
- G David S Hirst
- Division of Neuroscience, John Curtin School of Medical Research, Canberra, ACT, 0200, Australia.
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