Altered expression of the glutamate transporter EAAC1 in neurons and immature oligodendrocytes after transient forebrain ischemia

Glutamate uptake is reduced during ischemia because of perturbations of ion ic gradients across neuronal and glial membranes. Using immunohistochemical and Western blot analyses, the authors examined the expression of the glut amate transporters EAAC1, GLAST, and GLT-1 in the rat hippocampus and cereb ral cortex 8 hours and 1 to 28 days after transient forebrain ischemia. Den sitometric analysis of immunoblots of CA1 homogenates showed a moderate inc rease in EAAC1 protein levels early after the insult. Consistently, it was observed that EAAC1 immunostaining in CA1 pyramidal neurons was more intens e after 8 hours and 1 day of reperfusion and reduced at later postischemia stages. A similar transient increase of EAAC1 immunolabeling was detected i n layer V pyramidal neurons of the cerebral cortex. In addition, the author s observed that EAAC1 also was located in oligodendroglial progenitor cells in subcortical white matter. The number of EAAC1-labeled cells in this reg ion was increased after 3 and 28 days of reperfusion. Finally, changes in G LAST and GLT-1 expression were not observed in the CA1 region after ischemi a using immunohistochemical study or immunoblotting. Enhanced expression of EAAC1 may be an adaptive response to increased levels of extracellular glu tamate during ischemia.