Ouabain‐induced reversal of astrocytic GLT‐1 crucial to neuronal death in neuron/astrocyte co‐cultures

Abstract

AbstractWe investigated whether the role of the astrocytic glutamate transporter GLT‐1 is reversed when the ionic gradient across plasma membrane has collapsed, and if so, whether the reversal is crucial to neuronal death. To estimate the direction of glutamate transport by GLT‐1, Na+ movement coupled with glutamate transport in astrocytes was analyzed in mixed astrocyte/neuron cultures. The rise in astrocytic intracellular Na+ due to glutamate exposure was suppressed by co‐treatment with dihydrokainate (DHK). In contrast, the ouabain‐induced rise in Na+ was significantly enhanced by DHK, suggesting that the role of GLT‐1 was reversed. We then analyzed whether the reversal increased the amount of extracellular glutamate, and was crucial to excitotoxic neuronal death. Ouabain treatment resulted in a marked rise in glutamate and in neuronal death, and both the rise and cell death were significantly attenuated by DHK treatment.