Antisense Knockdown of Glutamate Transporters Alters the Subfield Selectivity of Kainate‐Induced Cell Death in Rat Hippocampal Slice Cultures

Abstract

Organotypic rat hippocampal slice cultures were used to study the role of excitatory amino acid transporters (EAATs) in kainate-induced cell death. Expression of the neuronal (EAAT3) or glial (EAAT2) transporters was inhibited with antisense phosphothioate oligonucleotides, and cytotoxicity was assessed with propidium iodide uptake. In control cultures, a concentration of 10 microM kainate was more cytotoxic in CA3 than in CA1. Treatment for 24 h with EAAT3 antisense oligonucleotide decreased kainate toxicity in CA1 but had an opposite effect in CA3. Neither antisense oligonucleotide to EAAT2 nor mismatch oligonucleotide to EAAT3 decreased kainate toxicity in CA1. Immunoblotting with affinity-purified antibodies showed that EAAT3 antisense oligonucleotide decreased selectively EAAT3 but not EAAT2 protein levels, and vice versa. NMDA was more cytotoxic in CA1 than in CA3, and antisense oligonucleotides to either EAAT3 or EAAT2 did not decrease the NMDA effect in CA1 or CA3. Dihydrokainate and DL-threo-beta-hydroxyaspartic acid were more cytotoxic in CA1 than in CA3, suggesting that the higher vulnerability of CA3 to kainate was not the result of its activity as transporter blocker. We conclude that glutamate transporters differentially regulate excitotoxicity in different hippocampal subfields.