Basic Cardiac Electrophysiology: Excitable Membranes

Jaye, Deborah A.; Xiao, Yong‐Fu; Sigg, Daniel C.

doi:10.1007/978-1-4419-6658-2_2

Cited by 9 publications

(8 citation statements)

References 5 publications

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“…This illustrates the crucial role of Na + permeability in the cochlea. In many excitable cell types, such as neurons and muscle cells, only slight Na + permeability is observed in the resting state, and it increases when an action potential is produced [4,11,15,28]. Some nonexcitable cell types, including renal epithelial cells, exhibit significant Na + permeability, but it is less than other ion permeabilities [30].…”

Section: Discussionmentioning

confidence: 99%

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The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential

Yoshida

Nin

Murakami

et al. 2016

Pflugers Arch - Eur J Physiol

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Eukaryotic cells exhibit negative resting membrane potential (RMP) owing to the high K(+) permeability of the plasma membrane and the asymmetric [K(+)] between the extracellular and intracellular compartments. However, cochlear fibrocytes, which comprise the basolateral surface of a multilayer epithelial-like tissue, exhibit a RMP of +5 to +12 mV in vivo. This positive RMP is critical for the formation of an endocochlear potential (EP) of +80 mV in a K(+)-rich extracellular fluid, endolymph. The epithelial-like tissue bathes fibrocytes in a regular extracellular fluid, perilymph, and apically faces the endolymph. The EP, which is essential for hearing, represents the potential difference across the tissue. Using in vivo electrophysiological approaches, we describe a potential mechanism underlying the unusual RMP of guinea pig fibrocytes. The RMP was +9.0 ± 3.7 mV when fibrocytes were exposed to an artificial control perilymph (n = 28 cochleae). Perilymphatic perfusion of a solution containing low [Na(+)] (1 mM) markedly hyperpolarized the RMP to -31.1 ± 11.2 mV (n = 10; p < 0.0001 versus the control, Tukey-Kramer test after one-way ANOVA). Accordingly, the EP decreased. Little change in RMP was observed when the cells were treated with a high [K(+)] of 30 mM (+10.4 ± 2.3 mV; n = 7; p = 0.942 versus the control). During the infusion of a low [Cl(-)] solution (2.4 mM), the RMP moderately hyperpolarized to -0.9 ± 3.4 mV (n = 5; p < 0.01 versus the control), although the membranes, if governed by Cl(-) permeability, should be depolarized. These observations imply that the fibrocyte membranes are more permeable to Na(+) than K(+) and Cl(-), and this unique profile and [Na(+)] gradient across the membranes contribute to the positive RMP.

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Section: Discussionmentioning

confidence: 99%

“…Excitable cells, such as neurons, cardiac myocytes, skeletal muscle cells, and smooth muscle cells, show an RMP of −50 to −90 mV, resulting from the high K + permeability of the membranes [11,15,28]. The negative RMP induced by K + permeability is also seen in non-excitable cells, including astroglia and retinal Müller cells [8].…”

Section: Introductionmentioning

confidence: 98%

The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential

Yoshida

Nin

Murakami

et al. 2016

Pflugers Arch - Eur J Physiol

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“…1). 2 Na C channel inactivation, recovery from inactivation, and associated deactivation further dictate the relative refractory period (RRP). The RRP describes a time period when sufficient Na C channels are available for reactivation and the V m is further repolarized so that a stronger stimulus may initiate the next AP.…”

Section: Introductionmentioning

confidence: 99%

“…The RRP describes a time period when sufficient Na C channels are available for reactivation and the V m is further repolarized so that a stronger stimulus may initiate the next AP. 2 When Na C channels do not inactivate completely, a measurable current of less than 0.5% of the peak current persists in the myocyte, known as late or persistent I Na . This current is sustained because it travels through Na C channels that do not inactivate completely, so they do not need go through recovery from inactivation.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and models of cardiac sodium channel inactivation

et al. 2017

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Shortly after cardiac Na channels activate and initiate the action potential, inactivation ensues within milliseconds, attenuating the peak Na current, I and allowing the cell membrane to repolarize. A very limited number of Na channels that do not inactivate carry a persistent I, or late I. While late I is only a small fraction of peak magnitude, it significantly prolongs ventricular action potential duration, which predisposes patients to arrhythmia. Here, we review our current understanding of inactivation mechanisms, their regulation, and how they have been modeled computationally. Based on this body of work, we conclude that inactivation and its connection to late I would be best modeled with a "feet-on-the-door" approach where multiple channel components participate in determining inactivation and late I. This model reflects experimental findings showing that perturbation of many channel locations can destabilize inactivation and cause pathological late I.

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“…That is, the information indicating whether cardiomyocytes contract or relax is encoded in the AP pulse train by the sinoatrial node. A successfully received AP pulse by a cardiomyocyte at rest causes this cardiomyocyte to contract, which is called as excitation-contraction coupling [23]. In contrast, when there is not any AP pulse received by a cardiomyocyte, corresponding cardiomyocyte stays at rest.…”

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confidence: 99%

An Information Theoretical Analysis of Nanoscale Molecular Gap Junction Communication Channel Between Cardiomyocytes

Kilinc

Akan

2013

IEEE Trans. Nanotechnology

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Molecular communication which is a promising paradigm to communicate at nanoscale is inspired by nature. One of the molecular communication methods in nature is the gap junction (GJ) communication between cardiomyocytes. The GJ communication is achieved by diffusion of ions through GJ channels between cardiomyocytes. Propagation of the cardiac action potential, is used for the transmission of information. For the first time in the literature, the GJ communication channel is modeled and analyzed from the information theoretical perspective to obtain the communication channel characteristics. For the information theoretical analysis, a closed form expression is derived for the capacity of the GJ communication channel. The channel capacity, propagation delay and information transmission rate are analyzed numerically. Results of the numerical analyses show that a decrease in the channel capacity, an increase in the propagation delay and either an increase or a decrease in the transmission rate are correlated with increased incidence of cardiac diseases. The method that we use and results that are presented in this paper may help in the investigation, diagnosis and treatment of cardiac diseases as well as help in the design of nanodevices communicating via GJ channels.

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Basic Cardiac Electrophysiology: Excitable Membranes

Cited by 9 publications

References 5 publications

The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential

The unique ion permeability profile of cochlear fibrocytes and its contribution to establishing their positive resting membrane potential

Mechanisms and models of cardiac sodium channel inactivation

An Information Theoretical Analysis of Nanoscale Molecular Gap Junction Communication Channel Between Cardiomyocytes

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