Antisense knockdown of glutamate transporters alters the subfield selectivity of kainate-induced cell death in rat hippocampal slice cultures

Organotypic rat hippocampal slice cultures were used to study the role of e xcitatory amino acid transporters (EAATs) in kainate-induced cell death. Ex pression of the neuronal (EAAT3) or glial (EAAT2) transporters was inhibite d with antisense phosphothioate oligonucleotides, and cytotoxicity was asse ssed with propidium iodide uptake. In control cultures, a concentration of 10 mu M kainate was more cytotoxic in CA3 than in CA1. Treatment For 24 h w ith EAAT3 antisense oligonucleotide decreased kainate toxicity in CA1 but h ad an opposite effect in CA3. Neither antisense oligonucleotide to EAAT2 no r mismatch oligonucleotide to EAAT3 decreased kainate toxicity in CA1. Immu noblotting with affinity-purified antibodies showed that EAAT3 antisense ol igonucleotide decreased selectively EAAT3 but not EAAT2 protein levels, and vice versa. NMDA was more cytotoxic in CA1 than in CA3, and antisense olig onucleotides to either EAAT3 or EAAT2 did not decrease the NMDA effect in C A1 or CA3. Dihydrokainate and DL-threo-beta-hydroxyaspartic acid were more cytotoxic in CA1 than in CA3, suggesting that the higher vulnerability of C A3 to kainate,was not the result of its activity as transporter blocker. We conclude that glutamate transporters differentially regulate excitotoxicit y in different hippocampal subfields.