Nonlinear effects in subthreshold virtual electrode polarization

Sambelashvili, Aleksandre; Nikolski, Vladimir P.; Efimov, Igor R.

doi:10.1152/ajpheart.00988.2002

Cited by 15 publications

(11 citation statements)

References 28 publications

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“…We did not observe the classically described dogbone-shaped potential distributions; however, we measured tissue responses at steady state, 200 ms after the stimulus onset. Others (39) have reported that low stimulus strength induces an initial dogbone-shaped field that spreads out nonuniformly, such that it can no longer be easily detected after 10 ms.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of conduction slowing during myocardial stretch by ventricular volume loading in the rabbit

Mills

Narayan²,

McCulloch³

2008

American Journal of Physiology-Heart and Circulatory Physiology

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Acute ventricular loading by volume inflation reversibly slows epicardial electrical conduction, but the underlying mechanism remains unclear. This study investigated the potential contributions of stretch-activated currents, alterations in resting membrane potential, or changes in intercellular resistance and membrane capacitance. Conduction velocity was assessed using optical mapping of isolated rabbit hearts at end-diastolic pressures of 0 and 30 mmHg. The addition of 50 microM Gd3+ (a stretch-activated channel blocker) to the perfusate had no effect on slowing. The effect of volume loading on conduction velocity was independent of changes in resting membrane potential created by altering the perfusate potassium concentration between 1.5 and 8 mM. Bidomain model analysis of optically recorded membrane potential responses to a unipolar stimulus suggested that the cross-fiber space constant and membrane capacitance both increased with loading (21%, P = 0.006, and 56%, P = 0.004, respectively), and these changes, when implemented in a resistively coupled one-dimensional network model, were consistent with the observed slowing (14%, P = 0.005). In conclusion, conduction slowing during ventricular volume loading is not attributable to stretch-activated currents or altered resting membrane potential, but a reduction of intercellular resistance with a concurrent increase of effective membrane capacitance results in a net slowing of conduction.

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Section: Discussionmentioning

confidence: 99%

Mechanisms of conduction slowing during myocardial stretch by ventricular volume loading in the rabbit

Mills

Narayan²,

McCulloch³

2008

American Journal of Physiology-Heart and Circulatory Physiology

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“…Sophisticated biophysical theories have been developed that predict the distribution of the transmembrane and extracellular potentials inside the heart during electrical shocks. Major successes were the prediction of the dog-bone-shaped polarization in anisotropic myocardial tissue (5)(6)(7), the formation of quatrefoil reentry (8), and qualitative patterns of surface polarization during defibrillation shocks in the whole heart (9). However, recent optical imaging studies utilizing voltage-sensitive dyes have revealed several major discrepancies between theory and experiment that cannot readily be resolved.…”

Section: Introductionmentioning

confidence: 99%

Probing Field-Induced Tissue Polarization Using Transillumination Fluorescent Imaging

Caldwell

Wellner

Mitrea

et al. 2010

Biophysical Journal

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Despite major successes of biophysical theories in predicting the effects of electrical shocks within the heart, recent optical mapping studies have revealed two major discrepancies between theory and experiment: 1), the presence of negative bulk polarization recorded during strong shocks; and 2), the unexpectedly small surface polarization under shock electrodes. There is little consensus as to whether these differences result from deficiencies of experimental techniques, artifacts of tissue damage, or deficiencies of existing theories. Here, we take advantage of recently developed near-infrared voltage-sensitive dyes and transillumination optical imaging to perform, for the first time that we know of, noninvasive probing of field effects deep inside the intact ventricular wall. This technique removes some of the limitations encountered in previous experimental studies. We explicitly demonstrate that deep inside intact myocardial tissue preparations, strong electrical shocks do produce considerable negative bulk polarization previously inferred from surface recordings. We also demonstrate that near-threshold diastolic field stimulation produces activation of deep myocardial layers 2-6 mm away from the cathodal surface, contrary to theory. Using bidomain simulations we explore factors that may improve the agreement between theory and experiment. We show that the inclusion of negative asymmetric current can qualitatively explain negative bulk polarization in a discontinuous bidomain model.

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“…Moreover, virtual electrodes predicted by the bidomain model have been demonstrated empirically over cardiac myocardium [60],[61]. Thus, the ability of a network of passive cable elements to generate VE, is well supported.…”

Section: Discussionmentioning

confidence: 83%

Electrotonic Signals along Intracellular Membranes May Interconnect Dendritic Spines and Nucleus

et al. 2008

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Synapses on dendritic spines of pyramidal neurons show a remarkable ability to induce phosphorylation of transcription factors at the nuclear level with a short latency, incompatible with a diffusion process from the dendritic spines to the nucleus. To account for these findings, we formulated a novel extension of the classical cable theory by considering the fact that the endoplasmic reticulum (ER) is an effective charge separator, forming an intrinsic compartment that extends from the spine to the nuclear membrane. We use realistic parameters to show that an electrotonic signal may be transmitted along the ER from the dendritic spines to the nucleus. We found that this type of signal transduction can additionally account for the remarkable ability of the cell nucleus to differentiate between depolarizing synaptic signals that originate from the dendritic spines and back-propagating action potentials. This study considers a novel computational role for dendritic spines, and sheds new light on how spines and ER may jointly create an additional level of processing within the single neuron.

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Nonlinear effects in subthreshold virtual electrode polarization

Cited by 15 publications

References 28 publications

Mechanisms of conduction slowing during myocardial stretch by ventricular volume loading in the rabbit

Mechanisms of conduction slowing during myocardial stretch by ventricular volume loading in the rabbit

Probing Field-Induced Tissue Polarization Using Transillumination Fluorescent Imaging

Electrotonic Signals along Intracellular Membranes May Interconnect Dendritic Spines and Nucleus

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