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Passive glial cells, fact or artifact?
1Department of Neurobiology, University of Alabama at Birmingham, 1719 6th Ave. S., CIRC Rm. 545, Birmingham, AL, USA.
The Journal of Membrane Biology
|December 8, 1998
Summary
Some astrocytes appear passive but can spontaneously unmask voltage-activated currents. This suggests they are not a distinct passive subpopulation, but rather their currents are transiently masked during recordings.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Astrocytes in rat hippocampus slices typically show voltage-activated Na+ and K+ currents.
- Some studies report astrocytes lacking these currents, proposing a passive subpopulation.
Purpose of the Study:
- To investigate the nature of astrocytes that appear electrophysiologically passive.
- To determine if these cells represent a distinct subpopulation or a transient state.
Main Methods:
- Whole-cell patch-clamp recordings in acute rat hippocampal slices and cultured astrocytes.
- Manipulation of extracellular calcium (Ca2+) and EGTA concentrations.
- Analysis of membrane capacitance and access resistance.
Main Results:
- Apparent passive astrocytes spontaneously unmasked voltage-activated currents during recordings.
- Low Ca2+/EGTA solutions reversibly suppressed K+ currents in cultured astrocytes.
- Current unmasking occurred without changes in membrane capacitance or access resistance, unlike recordings with poor cell access.
Conclusions:
- Electrophysiologically passive astrocytes do not represent a distinct subpopulation.
- Transient masking of voltage-activated currents by low Ca2+/EGTA or poor cell access explains the apparent passive state.
- These findings refine our understanding of astrocyte electrophysiology.