Timing the excitotoxic induction of heat shock protein 70 transcription.

The time course of heat-shock protein 70 (HSP70) transcriptional induction was compared with neuronal- and non-neuronal-specific mRNAs following intrastriatal quinolinate (QA) injection. Within one hour of QA exposure, immediate-early gene (IEG; c-fos) activation preceded slight increases in glutamic acid decaroxylase (GAD) mRNA levels. However, glial fibrillary acid protein (GFAP) and HSP70 mRNA levels remained constant. After one hour, HSP70 mRNA levels surged 6 fold during a delayed transcriptional phase that was induced between 4-12 hours. This phase was characterized by massive increases in c-fos and GFAP mRNAs while GAD transcripts fell drastically suggestive of neuronal death. Therefore HSP70 genes may play an important role in glial/immune activation following rapid excitotoxic damage by direct injections of quinolinate.