Gene expression of two glutamate receptor subunits in response to repeated stress exposure in rat hippocampus.

1. Glutamatergic mechanisms are thought to be involved in stress-induced alterations of brain function, especially in the hippocampus. We have hypothesized that repeated stress exposure may evoke changes of hippocampal glutamate receptors at the level of gene expression. 2. The study was designed to analyze the levels of mRNA coding for NMDAR1, the essential subunit of the N-methyl-D-aspartate (NMDA) receptor subtype, and for GluR1, an AMPA glutamate receptor subunit, after repeated immobilization stress in rat hippocampus. Toward this aim, we applied a competitive RT-PCR technique which allowed precise and reliable quantification of the transcripts. 3. We found that repeated immobilization stress for 7 days significantly increased GluR1 mRNA levels, by 27% (P<0.01), as measured 24 hr after the last stress exposure. Levels of mRNA coding for NMDAR1 were slightly elevated, but the difference failed to be significant. 4. These results demonstrate selective changes in the gene expression of glutamate receptor subunits, which are likely to take part in the mechanisms leading to enhanced excitability and vulnerability of hippocampal neurons and to potential damage during repeated or chronic stress exposure.