Na+ and K+ dependence of L-glutamate-induced suppression of astrocyte stellation in culture.

We have recently found that L-glutamate suppresses astrocyte stellation induced by various stimuli, and that this effect of L-glutamate is mimicked by transportable glutamate uptake inhibitors. To test the possible role of the glutamate transporter in the regulation of astrocyte morphology, we investigated the Na+ and K+ dependence of this effect of L-glutamate. In astrocyte cultures obtained from the cerebral cortex of neonatal rats, the L-glutamate-induced suppression of astrocyte stellation was significantly attenuated in a low- Na+/high- K+ medium and by the Na+ -K+ pump inhibitor ouabain. These results support that astrocyte morphology is affected by the activity of the Na+ -dependent glutamate transporter.