AMPA/kainate receptor activation blocks K+ currents via internal Na+ increase in mouse cultured stellate astrocytes
✍ Scribed by Antoine Robert; Pierre J. Magistretti
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 285 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0894-1491
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✦ Synopsis
Cultured mouse cortical astrocytes of the stellate type were studied by using the patch-clamp technique in whole-cell configuration. The astrocytes express at least two types of outwardly rectifying K 1 channels which mediate a transient and a sustained current. Activation of AMPA receptors by kainate leads to a substantial blockade of both types of K 1 currents. The blockade is absent when Na 1 is withdrawn from the external medium, suggesting that it is caused by constant Na 1 influx through AMPA receptors. The presence of high Na 1 solutions in the pipette induces a blockade of both K 1 currents which is very similar to the blockade induced by kainate, supporting thus the view that the mechanism of the blockade of K 1 channels by kainate involves Na 1 increases in the submembrane area. The blockade occurs between 20 and 40 mM [Na 1 ] i , which is within the physiological range of [Na 1 ] i in astrocytes. The data may suggest that the blockade of K 1 channels by high [Na 1 ] i conditions could provide a mechanism to prevent K 1 leakage from the astrocytes into the extracellular space during periods of intense neuronal activity.