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Intracellular chloride modulates A-type potassium currents in astrocytes
1Department of Physiology, University of Saskatchewan, Saskatoon, Canada.
Glia
|August 31, 2002
Summary
GABA(A) receptor agonist muscimol blocks astrocyte A-type potassium currents by altering activation kinetics. Intracellular chloride concentration influences these potassium currents, suggesting a role in modulating K(+) channel voltage sensors.
Area of Science:
- Neuroscience
- Cellular Physiology
- Molecular Biology
Background:
- Astrocytes express GABA(A) receptors.
- GABA(A) receptor activation influences ion currents in astrocytes.
Purpose of the Study:
- To investigate the effects of muscimol on astrocyte ion currents.
- To determine the role of chloride ions in modulating potassium currents.
Main Methods:
- Whole-cell and perforated patch-clamp electrophysiology in astrocytes.
- Application of muscimol and varying intracellular chloride concentrations.
- Barium application to isolate chloride currents.
Main Results:
- Muscimol application induced chloride currents and blocked inactivating A-type potassium currents.
- Low intracellular chloride reduced A-type current and shifted inactivation/activation kinetics.
- Estimated intracellular chloride concentration was 29 ± 3.2 mM.
- Chloride ions appear to modulate K(+) channel voltage sensor regions.
Conclusions:
- GABA(A) receptor activation in astrocytes affects both chloride and potassium currents.
- Intracellular chloride concentration is a key factor in modulating astrocyte A-type potassium currents.
- Chloride ions may influence K(+) channel gating by altering local membrane electric fields.