AMPA/kainate receptor activation blocks K+ currents via internal Na+ increase in mouse cultured stellate astrocytes

Glia. 1997 May;20(1):38-50.

Abstract

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+ 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+ currents. The blockade is absent when Na+ is withdrawn from the external medium, suggesting that it is caused by constant Na+ influx through AMPA receptors. The presence of high Na+ solutions in the pipette induces a blockade of both K+ currents which is very similar to the blockade induced by kainate, supporting thus the view that the mechanism of the blockade of K+ channels by kainate involves Na+ increases in the submembrane area. The blockade occurs between 20 and 40 mM [Na+]i, which is within the physiological range of [Na+]i in astrocytes. The data may suggest that the blockade of K+ channels by high [Na+]i conditions could provide a mechanism to prevent K+ leakage from the astrocytes into the extracellular space during periods of intense neuronal activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Astrocytes / cytology
  • Astrocytes / drug effects
  • Astrocytes / physiology*
  • Barium / pharmacology
  • Cells, Cultured
  • Cerebral Cortex / physiology*
  • Kainic Acid / pharmacology*
  • Membrane Potentials / drug effects
  • Mice
  • Patch-Clamp Techniques
  • Potassium Channel Blockers*
  • Potassium Channels / biosynthesis
  • Potassium Channels / physiology
  • Receptors, AMPA / drug effects
  • Receptors, AMPA / physiology*
  • Sodium / metabolism*
  • Sodium / pharmacology

Substances

  • Potassium Channel Blockers
  • Potassium Channels
  • Receptors, AMPA
  • Barium
  • Sodium
  • Kainic Acid