Sodium currents in mammalian muscle

Adrian, R. H.; Marshall, Michael W.

doi:10.1113/jphysiol.1977.sp011855

Cited by 107 publications

(94 citation statements)

References 23 publications

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“…Most of the results with intact fibers were obtained with the three-microelectrode method applied to the end of a fiber (Adrian et al, 1970). The only exception is the work of Hollingworth and Marshall (1981), who used the three-microelectrode method applied to the middle of a fiber (Adrian and Marshall, 1977). Movement in intact fibers was reduced by making the external solutions hyperosmotic with sucrose.…”

Section: Discussionmentioning

confidence: 99%

Intramembranous charge movement in frog cut twitch fibers mounted in a double vaseline-gap chamber.

Hui

Chandler

1990

The Journal of General Physiology

142

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Section: Discussionmentioning

confidence: 99%

Intramembranous charge movement in frog cut twitch fibers mounted in a double vaseline-gap chamber.

Hui

Chandler

1990

The Journal of General Physiology

142

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“…However, it would be a serious obstacle to analysis of the kinetics of slow inward current activation. Such analysis might be carried out more easily using the second difference method of Adrian & Marshall (1977), which measures current density in the vicinity of the nearer voltage electrode.…”

Section: Discussionmentioning

confidence: 99%

Three‐micro‐electrode voltage clamp experiments in calf cardiac Purkinje fibres: is slow inward current adequately measured?

Kass¹,

Siegelbaum²,

Tsien³

1979

The Journal of Physiology

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SUMMARY1. The three-micro-electrode voltage clamp method (Adrian, Chandler & Hodgkin, 1970) was adapted for the study of regenerative inward currents in cardiac muscle. The adequacy of measurements of slow inward current in cardiac Purkinje fibres was assessed.2. Membrane current density is reported simultaneously by total applied current (IT), along with a longitudinal voltage difference signal (A V), recorded between two intracellular micro-electrodes.3. Non-linear cable calculations show that A V is a more faithful measure of membrane current density than IT as peak inward current increases. Quantitative agreement between A V and IT only occurs when both signals report the membrane characteristics that would be obtained with an ideal longitudinal space clamp.4. Agreement between AV and IT is thus a useful criterion for satisfactory experimental measurements which we applied to the slow inward current. This component was elicited by depolarizing steps from a holding potential near -45 mV in the presence of tetrodotoxin. The IT signal was compared directly with A V/R, where R is an effective longitudinal resistance that was experimentally determined.5. AV/R and IT showed very good agreement in both peak amplitude and time course at all potentials studied.6. Radial non-uniformity during the measured peak slow inward current was estimated by calculations assuming clefts 200 A wide with a uniform distribution of ionic channels. The calculated voltage span from surface to centre was always less than 5 mV, and the measured I-V characteristics showed little distortion.7. In another check, I-V characteristics and slow response membrane action potentials were compared. The measured peak current showed good agreement with the product (total preparation capacitance) x (rate of rise).8. The experimental and theoretical analysis suggest that the measurements of slow inward current are a good approximation to genuine membrane properties.

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“…Recent experiments have shown that the membrane currents of mammalian muscle under voltage clamp are qualitatively similar to those of frog muscle (Pappone, 1977;Adrian & Marshall, 1977;Duval & Leoty, 1978). This paper presents a full account of the conductance changes during depolarization in cut pieces from fasttwitch rat skeletal muscle fibres studied using the vaseline-gap clamp.…”

Section: Introductionmentioning

confidence: 99%

Voltage‐clamp experiments in normal and denervated mammalian skeletal muscle fibres.

Pappone¹

1980

The Journal of Physiology

278

203

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SUMMARY1. The vaseline-gap voltage-clamp method has been applied to the study of ionic currents in cut pieces from innervated and 5-7 day denervated rat skeletal muscle fibres.2. Kinetic analysis of sodium currents in innervated rat muscle showed them to be similar to those in frog muscle, except that rat sodium channels are activated at slightly more negative potentials. Peak sodium conductances of 40-50 m-mho/cm2 were measured, corresponding to values of GNa of 100-120 m-mho/cm2.3. The permeability sequence of the sodium channel to several organic and inorganic cations is Li+ > Na+ > hydroxylammonium > hydrazinium > guanidiniumã mmonium > K+. TMA+ and Ca2+ were not measurably permeant.4. Denervation appears to shift activation and inactivation parameters of sodium currents by 10 mV to more negative potentials, but does not appreciably affect the maximum peak sodium conductance or the time constants for activation and inactivation.5. Dose-response curves for block by tetrodotoxin in innervated fibres are fitted well by assuming binding of toxin to a single population of channels with a dissociation constant of about 5 nm. In denervated fibres there appears in addition a second population of channels with a dissociation constant in the micromolar range. These relatively toxin-insensitive channels respond less rapidly to potential changes, and can contribute up to 25-30 0% of the total sodium conductance.6. The potassium currents of innervated rat muscle were similar to those of frog muscle in their voltage dependence of activation.7. The time constant for inactivation of the sodium current, Th, at -13 mV showed a temperature dependence measured between 10 and 20 'C equivalent to an average Q10 of 2*3. The Q1o for the time constant of activation of the potassium current, Tn, averaged 2-5 between -40 mV and + 40 mV, measured over the same temperature range.

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Sodium currents in mammalian muscle

Cited by 107 publications

References 23 publications

Intramembranous charge movement in frog cut twitch fibers mounted in a double vaseline-gap chamber.

Intramembranous charge movement in frog cut twitch fibers mounted in a double vaseline-gap chamber.

Three‐micro‐electrode voltage clamp experiments in calf cardiac Purkinje fibres: is slow inward current adequately measured?

Voltage‐clamp experiments in normal and denervated mammalian skeletal muscle fibres.

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