---
_id: '3475'
abstract:
- lang: eng
text: '1. A potassium channel activated by internal Na+ ions (K+Na channel) was
identified in peripheral myelinated axons of Xenopus laevis using the cell-attached
and excised configurations of the patch clamp technique. 2. The single-channel
conductance for the main open state was 88 pS with [K+]o = 105 mM and pS with
[K+]o = 2.5 mM ([K+]i = 105 mM). The channel was selectively permeable to K+ over
Na+ ions. A characteristic feature of the K+Na channel was the frequent occurrence
of subconductance states. 3. The open probability of the channel was strongly
dependent on the concentration of Na+ ions at the inner side of the membrane.
The half-maximal activating Na+ concentration and the Hill coefficient were 33
mM and 2.9, respectively. The open probability of the channel showed only weak
potential dependence. 4. The K+Na channel was relatively insensitive to external
tetraethylammonium (TEA+) in comparison with voltage-dependent axonal K+ channels;
the half-maximal inhibitory concentration (IC50) was 21.3 mM (at -90 mV). In contrast,
the channel was blocked by low concentrations of external Ba2+ and Cs+ ions, with
IC50 values of 0.7 and 1.1 mM, respectively (at -90 mV). The block by Ba2+ and
Cs+ was more pronounced at negative than at positive membrane potentials. 5. A
comparison of the number of K+Na 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+Na 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+Na channels may be involved in setting the resting
potential of vertebrate axons. Simulations of Na+ ion diffusion suggest two possible
mechanisms of activation of K+Na 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.'
acknowledgement: 'We thank Drs M.Häusser and A. Villarroel for critically reading
the manuscript, Dr E. v. Kitzing and A. Roth for many helpful discussions. This
work was supported by the Deutsche Forschungsgemeinschaft (Vo188/13-2). '
article_processing_charge: No
article_type: original
author:
- first_name: Duk
full_name: Koh, Duk
last_name: Koh
- first_name: Peter M
full_name: Jonas, Peter M
id: 353C1B58-F248-11E8-B48F-1D18A9856A87
last_name: Jonas
orcid: 0000-0001-5001-4804
- first_name: Werner
full_name: Vogel, Werner
last_name: Vogel
citation:
ama: Koh D, Jonas PM, Vogel W. Na+-activated K+ channels localized in the nodal
region of myelinated axons of Xenopus. Journal of Physiology. 1994;479:183-197.
doi:10.1113/jphysiol.1994.sp020287
apa: Koh, D., Jonas, P. M., & Vogel, W. (1994). Na+-activated K+ channels localized
in the nodal region of myelinated axons of Xenopus. Journal of Physiology.
Wiley-Blackwell. https://doi.org/10.1113/jphysiol.1994.sp020287
chicago: Koh, Duk, Peter M Jonas, and Werner Vogel. “Na+-Activated K+ Channels Localized
in the Nodal Region of Myelinated Axons of Xenopus.” Journal of Physiology.
Wiley-Blackwell, 1994. https://doi.org/10.1113/jphysiol.1994.sp020287.
ieee: D. Koh, P. M. Jonas, and W. Vogel, “Na+-activated K+ channels localized in
the nodal region of myelinated axons of Xenopus,” Journal of Physiology,
vol. 479. Wiley-Blackwell, pp. 183–197, 1994.
ista: Koh D, Jonas PM, Vogel W. 1994. Na+-activated K+ channels localized in the
nodal region of myelinated axons of Xenopus. Journal of Physiology. 479, 183–197.
mla: Koh, Duk, et al. “Na+-Activated K+ Channels Localized in the Nodal Region of
Myelinated Axons of Xenopus.” Journal of Physiology, vol. 479, Wiley-Blackwell,
1994, pp. 183–97, doi:10.1113/jphysiol.1994.sp020287.
short: D. Koh, P.M. Jonas, W. Vogel, Journal of Physiology 479 (1994) 183–197.
date_created: 2018-12-11T12:03:31Z
date_published: 1994-01-01T00:00:00Z
date_updated: 2022-06-03T11:09:21Z
day: '01'
doi: 10.1113/jphysiol.1994.sp020287
extern: '1'
external_id:
pmid:
- '7799220 '
intvolume: ' 479'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1155738/
month: '01'
oa: 1
oa_version: Published Version
page: 183 - 197
pmid: 1
publication: Journal of Physiology
publication_identifier:
issn:
- 0022-3751
publication_status: published
publisher: Wiley-Blackwell
publist_id: '2912'
quality_controlled: '1'
status: public
title: Na+-activated K+ channels localized in the nodal region of myelinated axons
of Xenopus
type: journal_article
user_id: ea97e931-d5af-11eb-85d4-e6957dddbf17
volume: 479
year: '1994'
...