The electrophysiological and mechanical effects of 2,3‐butane‐dione monoxime and cytochalasin‐D in the Langendorff perfused rabbit heart

Kettlewell, Sarah; Walker, Nicola L.; Cobbe, Stuart M.; Burton, Francis L.; Smith, Godfrey L.

doi:10.1113/expphysiol.2003.026732

Cited by 69 publications

(76 citation statements)

References 24 publications

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“…The use of two excitation wavelengths for Fura-2/AM-based Ca 2+ measurements further compounds this. Also, uncoupling contraction from excitation and Ca 2+ release is necessary for the current protocols; achieved by BDM and blebbistatin, but this may confound the morphology of APs and CaTs, especially in the whole-heart preparation [29], although minimal effects of BDM [30] and blebbistatin [31] have also been reported. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”

Section: Strengthsmentioning

confidence: 99%

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts

Ghouri

Kelly

Burton³

et al. 2013

Journal of Biophotonics

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We describe a novel two-photon (2P) laser scanning microscopy (2PLSM) protocol that provides ratiometric transmural measurements of membrane voltage (V m ) via Di-4-ANEPPS in intact mouse, rat and rabbit hearts with subcellular resolution. The same cells were then imaged with Fura-2/AM for intracellular Ca 2+ recordings. Action potentials (APs) were accurately characterized by 2PLSM vs microelectrodes, albeit fast events (<1ms) were sub-optimally acquired by 2PLSM due to limited sampling frequencies (2.6kHz). The slower Ca 2+ transient (CaT) time course (>1ms) could be accurately described by 2PLSM. In conclusion, V m -and Ca 2+ -sensitive dyes can be 2P excited within the cardiac muscle wall to provide AP and Ca 2+ signals to ~400μm.Abstract Figure: 2P-excited images of Di-4-ANEPPS-and Fura-2/AM-loaded myocardium including the resultant AP and CaT extracted from the presented protocols.

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Section: Strengthsmentioning

confidence: 99%

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts

Ghouri

Kelly

Burton³

et al. 2013

Journal of Biophotonics

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“…Then, 15 mmol/l 2,3-butanedione monoxime (SigmaAldrich) were used to eliminate motion artifact during optical recordings. The effects on conduction velocity and repolarization in rabbit ventricular myocardium at this concentration are minor (24). Two Ag/AgCl disc electrodes were placed in the center of the preparation, one on the epicardial side and the other on the endocardial side, and were used to record a pseudo-ECG from the chamber.…”

Section: Methodsmentioning

confidence: 99%

Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium

Myles

Bernus

Burton

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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Myles RC, Bernus O, Burton FL, Cobbe SM, Smith GL. Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium. Am J Physiol Heart Circ Physiol 299: H1812-H1822, 2010. First published October 1, 2010; doi:10.1152/ajpheart.00518.2010.-Although transmural heterogeneity of action potential duration (APD) is established in single cells isolated from different tissue layers, the extent to which it produces transmural gradients of repolarization in electrotonically coupled ventricular myocardium remains controversial. The purpose of this study was to examine the relative contribution of intrinsic cellular gradients of APD and electrotonic influences to transmural repolarization in rabbit ventricular myocardium. Transmural optical mapping was performed in left ventricular wedge preparations from eight rabbits. Transmural patterns of activation, repolarization, and APD were recorded during endocardial and epicardial stimulation. Experimental results were compared with modeled data during variations in electrotonic coupling. A transmural gradient of APD was evident during endocardial stimulation, which reflected differences previously seen in isolated cells, with the longest APD at the endocardium and the shortest at the epicardium (endo: 165 Ϯ 5 vs. epi: 147 Ϯ 4 ms; P Ͻ 0.05). During epicardial stimulation, this gradient reversed (epi: 162 Ϯ 4 vs. endo: 148 Ϯ 6 ms; P Ͻ 0.05). In both activation sequences, transmural repolarization followed activation and APD shortened along the activation path such that significant transmural gradients of repolarization did not occur. This correlation between transmural activation time and APD was recapitulated in simulations and varied with changes in intercellular coupling, confirming that it is mediated by electrotonic current flow between cells. These data suggest that electrotonic influences are important in determining the transmural repolarization sequence in rabbit ventricular myocardium and that they are sufficient to overcome intrinsic differences in the electrophysiological properties of the cells across the ventricular wall. action potential remodeling; electrophysiology TRANSMURAL DIFFERENCES in cellular electrophysiology are known to exist in mammalian ventricular myocardium (13,47). In studies of isolated ventricular myocytes, endocardial cells display an action potential duration (APD) that is consistently longer than that of epicardial cells (9,26,28,51). Furthermore, ventricular M cells with distinct electrophysiological characteristics have been identified in the midmyocardium of some mammals, including rabbit (26), dog (40), and human (10,19). At slow stimulation rates, M cells display an APD that is much longer than cells isolated from either epi-or endocardial regions. The dominant influence of these cellular electrophysiological heterogeneities in intact myocardium has been suggested by studies using microelectrode recordings from three regions on the transmural surface of isolated canine ve...

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“…Although the specificity of blebbistatin has been confirmed previously, 17 alterations in APD, conduction delay, and restitution characteristics have been reported with BDM. 18 To investigate the influence of uncouplers on AP characteristics, floating ME recordings were compared before and after perfusion of uncoupling agents ( Figure II …”

Section: Optical and Electric Ap Configurationmentioning

confidence: 99%

Subepicardial Action Potential Characteristics Are a Function of Depth and Activation Sequence in Isolated Rabbit Hearts

Kelly

Ghouri

Kemi

et al. 2013

Circ: Arrhythmia and Electrophysiology

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V entricular electric propagation is governed by activation sequence, electric properties of the myocardial syncytium, and anatomy of the ventricular wall.1,2 Time course and rate of propagation of the action potential (AP) depends on ionic current flow across sarcolemmal membranes and the electric resistance and capacitance of nearby myocardium. 3 These factors are heterogeneous across the ventricular wall; because of polarized gap junction distribution, intercellular resistance depends on myocardial fiber orientation 4 ; electrotonic load at any given point in the myocardium depends on the activation sequence and distance from structural features, such as the epicardial surface. In addition, ion channel expression is heterogeneous in the apex-base 5 and endocardial-epicardial axes. 6 Therefore, the rate of depolarization of the AP reflects myocardial excitability. However, the influence of activation sequence on AP upstroke is still a matter of debate. 7,8 Although continuous cable theory predicts that a higher conduction velocity (CV) is associated with higher maximal upstroke velocity (dV/dt max ), 9 on the surface of isolated cardiac muscle preparations longitudinal propagation results in faster CV but lower dV/dt max relative to transverse propagation. 10 These observations were explained by (1) predominantly axial connexin distribution and (2) arrangement of capillary vessels parallel to the longitudinal axis of the cells.11 This has been challenged by computational modeling, which suggests that differences in upstroke characteristics are limited to myocardium close to the epicardial surface.7 Until now, this could not be verified experimentally because of the technical difficulty associated with accurate transmembrane © 2013 American Heart Association, Inc. Original Article Circ Arrhythm ElectrophysiolBackground-Electric excitability in the ventricular wall is influenced by cellular electrophysiology and passive electric properties of the myocardium. Action potential (AP) rise time, an indicator of myocardial excitability, is influenced by conduction pattern and distance from the epicardial surface. This study examined AP rise times and conduction velocity as the depolarizing wavefront approaches the epicardial surface. Methods and Results-Two-photon excitation of di-4-aminonaphthenyl-pyridinum-propylsulfonate was used to measure electric activity at discrete epicardial layers of isolated Langendorff-perfused rabbit hearts to a depth of 500 μm. Endoto-epicardial wavefronts were studied during right atrial or ventricular endocardial pacing. Similar measurements were made with epi-to-endocardial, transverse, and longitudinal pacing protocols. Results were compared with data from a bidomain model of 3-dimensional (3D) electric propagation within ventricular myocardium. During right atrial and endocardial pacing, AP rise time (10%-90% of upstroke) decreased by ≈50% between 500 and 50 μm from the epicardial surface, whereas conduction velocity increased and AP duration was only slightly shorter (≈4%). The...

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The electrophysiological and mechanical effects of 2,3‐butane‐dione monoxime and cytochalasin‐D in the Langendorff perfused rabbit heart

Abstract: Procedures that reduce contraction are used to facilitate optical measurements of membrane potential, but it is unclear to what extent they affect the excitability of the heart. This study has examined the electrophysiological consequences of a range of extracellular

Cited by 69 publications

References 24 publications

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts

Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium

Subepicardial Action Potential Characteristics Are a Function of Depth and Activation Sequence in Isolated Rabbit Hearts

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The electrophysiological and mechanical effects of 2,3‐butane‐dione monoxime and cytochalasin‐D in the Langendorff perfused rabbit heart

Abstract: Procedures that reduce contraction are used to facilitate optical measurements of membrane potential, but it is unclear to what extent they affect the excitability of the heart. This study has examined the electrophysiological consequences of a range of extracellular

Cited by 69 publications

References 24 publications

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca2+ in intact mice, rat, and rabbit hearts

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca2+ in intact mice, rat, and rabbit hearts

Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium

Subepicardial Action Potential Characteristics Are a Function of Depth and Activation Sequence in Isolated Rabbit Hearts

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Product

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2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts

2‐photon excitation fluorescence microscopy enables deeper high‐resolution imaging of voltage and Ca²⁺ in intact mice, rat, and rabbit hearts