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Eur Biophys J
1990 Jan 01;186:317-26. doi: 10.1007/bf00196922.
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Open-channel block of Na+ channels by intracellular Mg2+.
Pusch M
.
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1. Macroscopic and single-channel currents through several types of cloned rat brain Na+ channels, expressed in Xenopus oocytes, were measured using the patch-clamp technique. 2. For all cloned channel types and for endogenous Na+ channels in chromaffin cells, intracellular Mg2+ blocks outward currents in a voltage-dependent manner similar to that in rat brain type II Na+ channel (Pusch et al. 1989). 3. A sodium-channel mutant ('cZ-2') with long single-channel open times was used to examine the voltage-dependent reduction of single-channel outward current amplitudes by intracellular Mg2+. This reduction could be described by a simple blocking mechanism with half-maximal blockage at 0 mV in 1.8 mM intracellular Mg2+ and a voltage-dependence of e-fold per 39 mV (in approximately 125 mM [Na]i); this corresponds to a binding-site at an electrical distance of 0.32 from the inside of the membrane. 4. At low Mg2+ concentrations and high voltages, the open-channel current variance is significantly elevated with respect to zero [Mg]i. This indicates that Mg2+ acts as a fast blocker rather than gradually decreasing current, e.g. by screening of surface charges. Analysis of the open-channel variance yielded estimates of the block and unblock rate constants, which are of the order of 2.10(8) M-1 S-1 and 3.6.10(5) S-1 at 0 mV for the mutant cZ-2. 5. A quantitative analysis of tail-currents of wild-type II channels showed that the apparent affinity for intracellular Mg2+ strongly depends on [Na]i. This effect could be explained in terms of a multi-ion pore model. 6. Simulated action potentials, calculated on the basis of the Hodgkin-Huxley theory, are significantly reduced in their amplitude and delayed in their onset by postulating Mg2+ block at physiological levels of [Mg]i.
Almers,
Voltage clamp of rat and human skeletal muscle: measurements with an improved loose-patch technique.
1984, Pubmed
Almers,
Voltage clamp of rat and human skeletal muscle: measurements with an improved loose-patch technique.
1984,
Pubmed
Begenisich,
Sodium channel permeation in squid axons. I: Reversal potential experiments.
1980,
Pubmed
Begenisich,
Sodium channel permeation in squid axons. II: Non-independence and current-voltage relations.
1980,
Pubmed
Bezanilla,
Inactivation of the sodium channel. I. Sodium current experiments.
1977,
Pubmed
Blatter,
Estimation of the upper limit of the free magnesium concentration measured with Mg-sensitive microelectrodes in ferret ventricular muscle: (1) use of the Nicolsky-Eisenman equation and (2) in calibrating solutions of the appropriate concentration.
1988,
Pubmed
Danko,
Block of sodium channels by internal mono- and divalent guanidinium analogues. Modulation by sodium ion concentration.
1986,
Pubmed
Fahlke,
Saturation effects and rectifier properties of sodium channels in human skeletal muscle.
1988,
Pubmed
Fenwick,
Sodium and calcium channels in bovine chromaffin cells.
1982,
Pubmed
Goldman,
POTENTIAL, IMPEDANCE, AND RECTIFICATION IN MEMBRANES.
1943,
Pubmed
Hamill,
Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches.
1981,
Pubmed
HODGKIN,
A quantitative description of membrane current and its application to conduction and excitation in nerve.
1952,
Pubmed
HODGKIN,
The effect of sodium ions on the electrical activity of giant axon of the squid.
1949,
Pubmed
Horie,
Voltage-dependent magnesium block of adenosine-triphosphate-sensitive potassium channel in guinea-pig ventricular cells.
1987,
Pubmed
Horie,
Rectification of muscarinic K+ current by magnesium ion in guinea pig atrial cells.
1987,
Pubmed
Ishihara,
The Mg2+ block and intrinsic gating underlying inward rectification of the K+ current in guinea-pig cardiac myocytes.
1989,
Pubmed
Kayano,
Primary structure of rat brain sodium channel III deduced from the cDNA sequence.
1988,
Pubmed
Matsuda,
Ohmic conductance through the inwardly rectifying K channel and blocking by internal Mg2+.
,
Pubmed
Mayer,
Voltage-dependent block by Mg2+ of NMDA responses in spinal cord neurones.
,
Pubmed
Methfessel,
Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels.
1986,
Pubmed
,
Xenbase
Noda,
Existence of distinct sodium channel messenger RNAs in rat brain.
,
Pubmed
Nowak,
Magnesium gates glutamate-activated channels in mouse central neurones.
,
Pubmed
Pappone,
Voltage-clamp experiments in normal and denervated mammalian skeletal muscle fibres.
1980,
Pubmed
Pusch,
Divalent cations as probes for structure-function relationships of cloned voltage-dependent sodium channels.
1990,
Pubmed
,
Xenbase
Pusch,
Intracellular magnesium blocks sodium outward currents in a voltage- and dose-dependent manner.
1989,
Pubmed
,
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Stühmer,
Patch clamp characterization of sodium channels expressed from rat brain cDNA.
1987,
Pubmed
,
Xenbase
Stühmer,
Structural parts involved in activation and inactivation of the sodium channel.
1989,
Pubmed
,
Xenbase
Woodhull,
Ionic blockage of sodium channels in nerve.
1973,
Pubmed
