Wirkung von Tetrodotoxin und Tetra�thylammoniumchlorid an der Innenseite der Schn�rringsmembran vonXenopus laevis

Koppenhöfer, E; Vogel, Werner

doi:10.1007/bf00593959

Cited by 66 publications

(14 citation statements)

References 29 publications

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“…The number of K'a channels in the patch was estimated from the maximum number of superimposed openings in the axon-attached and, subsequently, in the inside-out configuration. The channel activity in both recording modes was similar, presumably because Na+ ions had diffused into the nodal region through the cut-open ends of the nerve fibres (Koppenhofer & Vogel, 1969;Palti, Gold ( Fig. 6A).…”

Section: K+a Channelmentioning

confidence: 90%

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Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Koh

Jónás

Vogel

1994

The Journal of Physiology

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1. A potassium channel activated by internal Na+ ions (K'. channel) was identified in peripheral myelinated axons of Xenopus laevis using the cell-attached and excised configurations of the patch clamp technique. 5. A comparison of the number of ]K' channels in nodal and paranodal patches from the same axon revealed that the channel density was about 10-fold higher at the node of Ranvier than at the paranode. Moreover, a correlation between the number of K+N channels and voltage-dependent Na+ channels in the same patches was found, suggesting co-localization of both channel types.6. As weakly potential-dependent ('leakage') channels, axonal K'. channels may be involved in setting the resting potential of vertebrate axons. Simulations of Na+ ion diffusion suggest two possible mechanisms of activation of KM channels: the local increase of Na+ concentration in a cluster of Na+ channels during a single action potential or the accumulation in the intracellular axonal compartment during a train of action potentials.

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Section: K+a Channelmentioning

confidence: 90%

“…In contrast to the block by TEA', 1 mm external Ba2" at -90 mV reduced the channel activity without any noticeable effect on the single-channel conductance (Koppenhofer & Vogel, 1969;Palti, Gold ( Fig. 6A).…”

Section: K+a Channelmentioning

confidence: 96%

Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Koh

Jónás

Vogel

1994

The Journal of Physiology

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“…Such changes have been termed "slow" or "ultraslow" inactivation and have been reported for amphibian myelinated nerve fibers (52, 129,238,318,458), frog muscle (12), frog ventricular myocytes (132), and rat muscle (382,415). Slow changes in I Na following changes in membrane potential have also been observed in lobster, crayfish (378), Myxicola (392), and squid (1,75,76,287) axons, in the latter preparation even after block of fast inactivation by intra-axonal application of pronase (379).…”

Section: Slow Inactivationmentioning

confidence: 97%

Sodium Channel Inactivation: Molecular Determinants and Modulation

Ulbricht

2005

Physiological Reviews

271

222

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Voltage-gated sodium channels open (activate) when the membrane is depolarized and close on repolarization (deactivate) but also on continuing depolarization by a process termed inactivation, which leaves the channel refractory, i.e., unable to open again for a period of time. In the "classical" fast inactivation, this time is of the millisecond range, but it can last much longer (up to seconds) in a different slow type of inactivation. These two types of inactivation have different mechanisms located in different parts of the channel molecule: the fast inactivation at the cytoplasmic pore opening which can be closed by a hinged lid, the slow inactivation in other parts involving conformational changes of the pore. Fast inactivation is highly vulnerable and affected by many chemical agents, toxins, and proteolytic enzymes but also by the presence of beta-subunits of the channel molecule. Systematic studies of these modulating factors and of the effects of point mutations (experimental and in hereditary diseases) in the channel molecule have yielded a fairly consistent picture of the molecular background of fast inactivation, which for the slow inactivation is still lacking.

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“…From these results we infer the presence of two binding sites for TEA; one at the external mouth of the pore outside of the membrane field and the other at a site about 4/5 of the electrical distance inward from the external mouth. Similar external and internal binding sites for TEA occur in delayed rectifier K' channels in vertebrate myelinated axons (16,17) and molluscan neurons (18,19).…”

mentioning

confidence: 90%

Exchange of Conduction Pathways Between Two Related K ⁺ Channels

Hartmann

Kirsch

Drewe

et al. 1991

Science

377

143

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The structure of the ion conduction pathway or pore of voltage-gated ion channels is unknown, although the linker between the membrane spanning segments S5 and S6 has been suggested to form part of the pore in potassium channels. To test whether this region controls potassium channel conduction, a 21-amino acid segment of the S5-S6 linker was transplanted from the voltage-activated potassium channel NGK2 to another potassium channel DRK1, which has very different pore properties. In the resulting chimeric channel, the single channel conductance and blockade by external and internal tetraethylammonium (TEA) ion were characteristic of the donor NGK2 channel. Thus, this 21-amino acid segment controls the essential biophysical properties of the pore and may form the conduction pathway of these potassium channels.

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Wirkung von Tetrodotoxin und Tetra�thylammoniumchlorid an der Innenseite der Schn�rringsmembran vonXenopus laevis

Cited by 66 publications

References 29 publications

Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Sodium Channel Inactivation: Molecular Determinants and Modulation

Exchange of Conduction Pathways Between Two Related K ⁺ Channels

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Wirkung von Tetrodotoxin und Tetra�thylammoniumchlorid an der Innenseite der Schn�rringsmembran vonXenopus laevis

Cited by 66 publications

References 29 publications

Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Na(+)‐activated K+ channels localized in the nodal region of myelinated axons of Xenopus.

Sodium Channel Inactivation: Molecular Determinants and Modulation

Exchange of Conduction Pathways Between Two Related K + Channels

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Product

Resources

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Exchange of Conduction Pathways Between Two Related K ⁺ Channels