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Kodirov SA, Brachmann J, Safonova TA, Zhuravlev VL. Inactivation of Native K Channels. J Membr Biol 2021; 255:13-31. [PMID: 34383081 DOI: 10.1007/s00232-021-00195-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 06/30/2021] [Indexed: 01/12/2023]
Abstract
We have experimented with isolated cardiomyocytes of mollusks Helix. During the whole-cell patch-clamp recordings of K+ currents a considerable decrease in amplitude was observed upon repeated voltage steps at 0.96 Hz. For these experiments, ventricular cells were depolarized to identical + 20 mV from a holding potential of - 50 mV. The observed spontaneous inhibition of outward currents persisted in the presence of 4-aminopyridine, tetraethylammonium chloride or E-4031, the selective class III antiarrhythmic agent that blocks HERG channels. Similar tendency was retained when components of currents sensitive to either 4-AP or TEA were mathematically subtracted. Waveforms of currents sensitive to 1 and 10 micromolar concentration of E-4031 were distinct comprising prevailingly those activated during up to 200 ms pulses. The outward current activated by a voltage ramp at 60 mV x s-1 rate revealed an inward rectification around + 20 mV. This feature closely resembles those of the mammalian cardiac delayed rectifier IKr.
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Affiliation(s)
- Sodikdjon A Kodirov
- Department of Cardiology, Medical University Hospital Heidelberg, 69120, Heidelberg, Germany. .,Department of General Physiology, Saint Petersburg University, 199034, Saint Petersburg, Russia. .,Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, 02115, USA. .,Department of Biophysics, Saint Petersburg University, 199034, Saint Petersburg, Russia. .,Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de Lisboa, Avenida Professor Egas Moniz, 1649-028, Lisboa, Portugal.
| | - Johannes Brachmann
- Department of Cardiology, Medical University Hospital Heidelberg, 69120, Heidelberg, Germany
| | - Tatiana A Safonova
- Department of General Physiology, Saint Petersburg University, 199034, Saint Petersburg, Russia
| | - Vladimir L Zhuravlev
- Department of Cardiology, Medical University Hospital Heidelberg, 69120, Heidelberg, Germany.,Department of General Physiology, Saint Petersburg University, 199034, Saint Petersburg, Russia
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2
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Mishra RC, Rahman MM, Davis MJ, Wulff H, Hill MA, Braun AP. Alpha 1 -adrenergic stimulation selectively enhances endothelium-mediated vasodilation in rat cremaster arteries. Physiol Rep 2019; 6:e13703. [PMID: 29756401 PMCID: PMC5949301 DOI: 10.14814/phy2.13703] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Revised: 03/19/2018] [Accepted: 04/16/2018] [Indexed: 11/24/2022] Open
Abstract
We have systematically investigated how vascular smooth muscle α1‐adrenoceptor activation impacts endothelium‐mediated vasodilation in isolated, myogenically active, rat cremaster muscle 1A arteries. Cannulated cremaster arteries were pressurized intraluminally to 70 mmHg to induce myogenic tone, and exposed to vasoactive agents via bath superfusion at 34°C. Smooth muscle membrane potential was measured via sharp microelectrode recordings in pressurized, myogenic arteries. The α1‐adrenergic agonist phenylephrine (25–100 nmol/L) produced further constriction of myogenic arteries, but did not alter the vasorelaxant responses to acetylcholine (0.3 μmol/L), SKA‐31 (an activator of endothelial Ca2+‐dependent K+ channels) (3 μmol/L) or sodium nitroprusside (10 μmol/L). Exposure to 0.25–1 μmol/L phenylephrine or 1 μmol/L norepinephrine generated more robust constrictions, and also enhanced the vasodilations evoked by acetylcholine and SKA‐31, but not by sodium nitroprusside. In contrast, the thromboxane receptor agonist U46619 (250 nmol/L) dampened responses to all three vasodilators. Phenylephrine exposure depolarized myogenic arteries, and mimicking this effect with 4‐aminopyridine (1 mmol/L) was sufficient to augment the SKA‐31‐evoked vasodilation. Inhibition of L‐type Ca2+ channels by 1 μmol/L nifedipine decreased myogenic tone, phenylephrine‐induced constriction and prevented α1‐adrenergic enhancement of endothelium‐evoked vasodilation; these latter deficits were overcome by exposure to 3 and 10 μmol/L phenylephrine. Mechanistically, augmentation of ACh‐evoked dilation by phenylephrine was dampened by eNOS inhibition and abolished by blockade of endothelial KCa channels. Collectively, these data suggest that increasing α1‐adrenoceptor activation beyond a threshold level augments endothelium‐evoked vasodilation, likely by triggering transcellular signaling between smooth muscle and the endothelium. Physiologically, this negative feedback process may serve as a “brake” to limit the extent of vasoconstriction in the skeletal microcirculation evoked by the elevated sympathetic tone.
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Affiliation(s)
- Ramesh C Mishra
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Mohammad M Rahman
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Michael J Davis
- Dalton Cardiovascular Research Institute and Dept. of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
| | - Heike Wulff
- Department of Pharmacology, University of California Davis, Davis, California
| | - Michael A Hill
- Dalton Cardiovascular Research Institute and Dept. of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri
| | - Andrew P Braun
- Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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3
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Ma D, Liu Z, Loh LJ, Zhao Y, Li G, Liew R, Islam O, Wu J, Chung YY, Teo WS, Ching CK, Tan BY, Chong D, Ho KL, Lim P, Yong RYY, Panama BK, Kaplan AD, Bett GCL, Ware J, Bezzina CR, Verkerk AO, Cook SA, Rasmusson RL, Wei H. Identification of an I Na-dependent and I to-mediated proarrhythmic mechanism in cardiomyocytes derived from pluripotent stem cells of a Brugada syndrome patient. Sci Rep 2018; 8:11246. [PMID: 30050137 PMCID: PMC6062539 DOI: 10.1038/s41598-018-29574-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 07/16/2018] [Indexed: 02/08/2023] Open
Abstract
Brugada syndrome (BrS) is an inherited cardiac arrhythmia commonly associated with SCN5A mutations, yet its ionic mechanisms remain unclear due to a lack of cellular models. Here, we used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a BrS patient (BrS1) to evaluate the roles of Na+ currents (INa) and transient outward K+ currents (Ito) in BrS induced action potential (AP) changes. To understand the role of these current changes in repolarization we employed dynamic clamp to “electronically express” IK1 and restore normal resting membrane potentials and allow normal recovery of the inactivating currents, INa, ICa and Ito. HiPSC-CMs were generated from BrS1 with a compound SCN5A mutation (p. A226V & p. R1629X) and a healthy sibling control (CON1). Genome edited hiPSC-CMs (BrS2) with a milder p. T1620M mutation and a commercial control (CON2) were also studied. CON1, CON2 and BrS2, had unaltered peak INa amplitudes, and normal APs whereas BrS1, with over 75% loss of INa, displayed a loss-of-INa basal AP morphology (at 1.0 Hz) manifested by a reduced maximum upstroke velocity (by ~80%, p < 0.001) and AP amplitude (p < 0.001), and an increased phase-1 repolarization pro-arrhythmic AP morphology (at 0.1 Hz) in ~25% of cells characterized by marked APD shortening (~65% shortening, p < 0.001). Moreover, Ito densities of BrS1 and CON1 were comparable and increased from 1.0 Hz to 0.1 Hz by ~ 100%. These data indicate that a repolarization deficit could be a mechanism underlying BrS.
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Affiliation(s)
- Dongrui Ma
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Zhenfeng Liu
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Li Jun Loh
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Yongxing Zhao
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Guang Li
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Reginald Liew
- Cardiovascular & Metabolic Disorders Program, Duke-NUS Medical School Singapore, Singapore, 169857, Republic of Singapore
| | - Omedul Islam
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Jianjun Wu
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Ying Ying Chung
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Wee Siong Teo
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Chi Keong Ching
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Boon Yew Tan
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Daniel Chong
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Kah Leng Ho
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Paul Lim
- Department of Cardiology, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore
| | - Rita Yu Yin Yong
- Defense Medical and Environmental Research Institute, DSO National Laboratories, Singapore, 117510, Republic of Singapore
| | - Brian K Panama
- University at Buffalo, State University of New York, Buffalo, NY, 14214, USA
| | - Aaron D Kaplan
- University at Buffalo, State University of New York, Buffalo, NY, 14214, USA
| | - Glenna C L Bett
- University at Buffalo, State University of New York, Buffalo, NY, 14214, USA
| | - James Ware
- Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Connie R Bezzina
- Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Arie O Verkerk
- Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Stuart A Cook
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore.,Cardiovascular & Metabolic Disorders Program, Duke-NUS Medical School Singapore, Singapore, 169857, Republic of Singapore.,Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Randall L Rasmusson
- University at Buffalo, State University of New York, Buffalo, NY, 14214, USA.
| | - Heming Wei
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, 169609, Republic of Singapore. .,Cardiovascular & Metabolic Disorders Program, Duke-NUS Medical School Singapore, Singapore, 169857, Republic of Singapore.
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4
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Odawara A, Matsuda N, Ishibashi Y, Yokoi R, Suzuki I. Toxicological evaluation of convulsant and anticonvulsant drugs in human induced pluripotent stem cell-derived cortical neuronal networks using an MEA system. Sci Rep 2018; 8:10416. [PMID: 29991696 PMCID: PMC6039442 DOI: 10.1038/s41598-018-28835-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 07/02/2018] [Indexed: 12/14/2022] Open
Abstract
Functional evaluation assays using human induced pluripotent stem cell (hiPSC)-derived neurons can predict the convulsion toxicity of new drugs and the neurological effects of antiepileptic drugs. However, differences in responsiveness depending on convulsant type and antiepileptic drugs, and an evaluation index capable of comparing in vitro responses with in vivo responses are not well known. We observed the difference in synchronized burst patterns in the epileptiform activities induced by pentylentetrazole (PTZ) and 4-aminopryridine (4-AP) with different action mechanisms using multi-electrode arrays (MEAs); we also observed that 100 µM of the antiepileptic drug phenytoin suppressed epileptiform activities induced by PTZ, but increased those induced by 4-AP. To compare in vitro results with in vivo convulsive responses, frequency analysis of below 250 Hz, excluding the spike component, was performed. The in vivo convulsive firing enhancement of the high γ wave and β wave component were observed remarkably in in vitro hiPSC-derived neurons with astrocytes in co-culture. MEA measurement of hiPSC-derived neurons in co-culture with astrocytes and our analysis methods, including frequency analysis, appear effective for predicting convulsion toxicity, side effects, and their mechanism of action as well as the comparison of convulsions induced in vivo.
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Affiliation(s)
- A Odawara
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi, 982-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, 982-8577, Japan.,Japan Society for the Promotion of Science, Tokyo, Japan
| | - N Matsuda
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi, 982-8577, Japan
| | - Y Ishibashi
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi, 982-8577, Japan
| | - R Yokoi
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi, 982-8577, Japan
| | - I Suzuki
- Department of Electronics, Graduate School of Engineering, Tohoku Institute of Technology, 35-1 Yagiyama Kasumicho, Taihaku-ku, Sendai, Miyagi, 982-8577, Japan. .,iPS-non-Clinical Experiments for Nervous System (iNCENS) Project, Kanagawa, Japan. .,Consortium for Safety Assessment using Human iPS Cells (CSAHi), Kanagawa, Japan.
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5
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Ortega FA, Grandi E, Krogh-Madsen T, Christini DJ. Applications of Dynamic Clamp to Cardiac Arrhythmia Research: Role in Drug Target Discovery and Safety Pharmacology Testing. Front Physiol 2018; 8:1099. [PMID: 29354069 PMCID: PMC5758594 DOI: 10.3389/fphys.2017.01099] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 12/13/2017] [Indexed: 12/31/2022] Open
Abstract
Dynamic clamp, a hybrid-computational-experimental technique that has been used to elucidate ionic mechanisms underlying cardiac electrophysiology, is emerging as a promising tool in the discovery of potential anti-arrhythmic targets and in pharmacological safety testing. Through the injection of computationally simulated conductances into isolated cardiomyocytes in a real-time continuous loop, dynamic clamp has greatly expanded the capabilities of patch clamp outside traditional static voltage and current protocols. Recent applications include fine manipulation of injected artificial conductances to identify promising drug targets in the prevention of arrhythmia and the direct testing of model-based hypotheses. Furthermore, dynamic clamp has been used to enhance existing experimental models by addressing their intrinsic limitations, which increased predictive power in identifying pro-arrhythmic pharmacological compounds. Here, we review the recent advances of the dynamic clamp technique in cardiac electrophysiology with a focus on its future role in the development of safety testing and discovery of anti-arrhythmic drugs.
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Affiliation(s)
- Francis A Ortega
- Physiology, Biophysics, and Systems Biology Graduate Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, United States
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA, United States
| | - Trine Krogh-Madsen
- Greenberg Division of Cardiology, Weill Cornell Medical College, New York, NY, United States
| | - David J Christini
- Physiology, Biophysics, and Systems Biology Graduate Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, United States.,Greenberg Division of Cardiology, Weill Cornell Medical College, New York, NY, United States
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6
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Golovko V, Gonotkov M, Lebedeva E. Effects of 4-aminopyridine on action potentials generation in mouse sinoauricular node strips. Physiol Rep 2015; 3:3/7/e12447. [PMID: 26156968 PMCID: PMC4552527 DOI: 10.14814/phy2.12447] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The physiological role of Ito has yet to be clarified. The goal of this study is to investigate the possible contribution of the transient outward current (Ito) on the generation of transmembrane action potentials (APs) and the sensitivity of mouse sinoauricular node (SAN) cells to a 4-aminopyridine (4AP) as Ito blocker. The electrophysiological identification of cells was performed in the sinoauricular node artery area (nstrips = 38) of the subendocardial surface using microelectrode technique. In this study, for the first time, it was observed that dependence duration of action potential at the level of 20% repolarization (APD20) level under a 4AP concentration in the pacemaker SAN and auricular cells corresponds to a curve predicted by Hill's equation. APD20 raised by 70% and spike duration of AP increased by 15-25%, when 4AP concentration was increased from 0.1 to 5.0 mmol/L. Auricular cells were found to be more sensitive to 4AP than true pacemaker cells. This was accompanied by a decrease in the upstroke velocity as compared to the control. Our data and previous findings in the literature lead us to hypothesize that the 4AP-sensitive current participates in the repolarization formation of pacemaker and auricular type cells. Thus, study concerning the inhibitory effects of lidocaine and TTX on APD20 can explain the phenomenon of the decrease in upstroke velocity, which, for the first time, was observed after exposure to 4AP. Duration of AP at the level of 20% repolarization (APD20) under a 4-AP concentration 0.5 mmol/L in the true pacemaker cells lengthen by 60-70% with a control.
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Affiliation(s)
- Vladimir Golovko
- Laboratory of Heart Physiology, Institute of Physiology, Komi Science Center, The Urals Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Mikhail Gonotkov
- Laboratory of Heart Physiology, Institute of Physiology, Komi Science Center, The Urals Branch of the Russian Academy of Sciences, Syktyvkar, Russia
| | - Elena Lebedeva
- Laboratory of Heart Physiology, Institute of Physiology, Komi Science Center, The Urals Branch of the Russian Academy of Sciences, Syktyvkar, Russia
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7
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Nguyen TP, Singh N, Xie Y, Qu Z, Weiss JN. Repolarization reserve evolves dynamically during the cardiac action potential: effects of transient outward currents on early afterdepolarizations. Circ Arrhythm Electrophysiol 2015; 8:694-702. [PMID: 25772542 DOI: 10.1161/circep.114.002451] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 02/20/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Transient outward K currents (Ito) have been reported both to suppress and to facilitate early afterdepolarizations (EADs) when repolarization reserve is reduced. Here, we used the dynamic clamp technique to analyze how Ito accounts for these paradoxical effects on EADs by influencing the dynamic evolution of repolarization reserve during the action potential. METHODS AND RESULTS Isolated patch-clamped rabbit ventricular myocytes were exposed to either oxidative stress (H2O2) or hypokalemia to induce bradycardia-dependent EADs at a long pacing cycle length of 6 s, when native rabbit Ito is substantial. EADs disappeared when the pacing cycle length was shortened to 1 s, when Ito becomes negligible because of incomplete recovery from inactivation. During 6-s pacing cycle length, EADs were blocked by the Ito blocker 4-aminopyridine, but reappeared when a virtual current with appropriate Ito-like properties was reintroduced using the dynamic clamp (n=141 trials). During 1-s pacing cycle length in the absence of 4-aminopyridine, adding a virtual Ito-like current (n=1113 trials) caused EADs to reappear over a wide range of Ito conductance (0.005-0.15 nS/pF), particularly when inactivation kinetics were slow (τinact≥20 ms) and the pedestal (noninactivating component) was small (<25% of peak Ito). Faster inactivation or larger pedestals tended to suppress EADs. CONCLUSIONS Repolarization reserve evolves dynamically during the cardiac action potential. Whereas sufficiently large Ito can suppress EADs, a wide range of intermediate Ito properties can promote EADs by influencing the temporal evolution of other currents affecting late repolarization reserve. These findings raise caution in targeting Ito as an antiarrhythmic strategy.
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Affiliation(s)
- Thao P Nguyen
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles.
| | - Neha Singh
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - Yuanfang Xie
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - Zhilin Qu
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - James N Weiss
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
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8
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Aminopyridine lengthened the plateau phase of action potentials in mouse sinoatrial node cells. Bull Exp Biol Med 2013; 156:4-6. [PMID: 24319724 DOI: 10.1007/s10517-013-2263-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Duration of the plateau phase (phase 2) of action potentials in pacemaker cells in mouse sinoatrial node characterized by low upstroke rate during the rapid depolarization (dV/dt max <7 V/sec, phase 0) and in atrial-like cells with dV/dt max <100 V/sec were prolonged by 50% with 4-aminopyridine in concentrations of 0.7 and 0.1 mM, respectively. This blocker did not lengthen the terminal repolarization (phase 3). The above changes were accompanied by a 20-80% decrease in dV/dt max in comparison to the control. It is hypothesized that the short-term (transient) outward current Ito takes a part in the plateau formation and modulates the duration of the rapid depolarization phase of action potentials in mouse sinoatrial node cells.
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9
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Metabolic syndrome remodels electrical activity of the sinoatrial node and produces arrhythmias in rats. PLoS One 2013; 8:e76534. [PMID: 24250786 PMCID: PMC3826723 DOI: 10.1371/journal.pone.0076534] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 09/01/2013] [Indexed: 01/08/2023] Open
Abstract
In the last ten years, the incidences of metabolic syndrome and supraventricular arrhythmias have greatly increased. The metabolic syndrome is a cluster of alterations, which include obesity, hypertension, hypertriglyceridemia, glucose intolerance and insulin resistance, that increase the risk of developing, among others, atrial and nodal arrhythmias. The aim of this study is to demonstrate that metabolic syndrome induces electrical remodeling of the sinus node and produces arrhythmias. We induced metabolic syndrome in 2-month-old male Wistar rats by administering 20% sucrose in the drinking water. Eight weeks later, the rats were anesthetized and the electrocardiogram was recorded, revealing the presence of arrhythmias only in treated rats. Using conventional microelectrode and voltage clamp techniques, we analyzed the electrical activity of the sinoatrial node. We observed that in the sinoatrial node of “metabolic syndrome rats”, compared to controls, the spontaneous firing of all cells decreased, while the slope of the diastolic depolarization increased only in latent pacemaker cells. Accordingly, the pacemaker currents If and Ist increased. Furthermore, histological analysis showed a large amount of fat surrounding nodal cardiomyocytes and a rise in the sympathetic innervation. Finally, Poincaré plot denoted irregularity in the R-R and P-P ECG intervals, in agreement with the variability of nodal firing potential recorded in metabolic syndrome rats. We conclude that metabolic syndrome produces a dysfunction SA node by disrupting normal architecture and the electrical activity, which could explain the onset of arrhythmias in rats.
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10
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Aréchiga-Figueroa IA, Rodríguez-Martínez M, Sánchez-Chapula JA. Voltage-dependent potassium currents in feline sino-atrial node myocytes. Pflugers Arch 2011; 462:385-96. [DOI: 10.1007/s00424-011-0984-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/30/2011] [Accepted: 06/06/2011] [Indexed: 11/28/2022]
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11
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Rodríguez-Martínez M, Aréchiga-Figueroa IA, Moreno-Galindo EG, Navarro-Polanco RA, Sánchez-Chapula JA. Muscarinic-activated potassium current mediates the negative chronotropic effect of pilocarpine on the rabbit sinoatrial node. Pflugers Arch 2011; 462:235-43. [PMID: 21487692 DOI: 10.1007/s00424-011-0962-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 03/23/2011] [Accepted: 03/28/2011] [Indexed: 11/28/2022]
Abstract
Pilocarpine is a nonspecific agonist of muscarinic receptors which was recently found to activate the M(2) receptor subtype in a voltage-dependent manner. The purpose of our study was to investigate the role of the acetylcholine (muscarinic)-activated K(+) current (I (KACh)) on the negative chronotropic effect of pilocarpine in rabbit sinoatrial node. In multicellular preparations, we studied the effect of pilocarpine on spontaneous action potentials. In isolated myocytes, using the patch clamp technique, we studied the effects of pilocarpine on I (KACh). Pilocarpine produced a decrease in spontaneous frequency, hyperpolarization of the maximum diastolic potential, and a decrease in the diastolic depolarization rate. These effects were partially antagonized by tertiapin Q. Cesium and calyculin A in the presence of tertiapin Q partially prevented the effects of pilocarpine. In isolated myocytes, pilocarpine activated the muscarinic potassium current, I (KACh) in a voltage-dependent manner. In conclusion, the negative chronotropic effects of pilocarpine on the sinatrial node could be mainly explained by activation of I (KACh).
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