Differential alteration of NMDA receptor subunits in the gerbil dentate gyrus and subiculum following seizure

In the present study, a chronological and comparative analysis of the immun oreactivities of N-methyl-D-aspartate (NMDA) receptor subunits in hippocamp us; of both seizure resistant (SR) and seizure sensitive (SS) gerbils was m ade in order to clarify, the temporal and spatial alterations of NMDA recep tor subunit expressions in the hippocampus complex. The changes in NMDA rec eptor immunoreactivity in the hippocampi of SS gerbils were restricted to b oth the dentate gyrus and the subiculum. At 30 min postictal, a decline in NMDA receptor subunit 1 (NR1) immunoreactivity in the suprablade of dentate gyrus was observed. This is in contrast to the enhancement of its immunode nsity in the infrablade. At 3 h postietal the NRL immunoreactivity in the i nfrablade also declined significantly. At 12 h postietal, its immunoreactiv ity in the hilar neurons was reduced. The NMDA receptor subunit 2A/B (NR2A/ B) immunoreactivity did not alter until 12 h following seizure-onset, when it was slightly decreased in the granule cells and hilar neurons. In the su biculum, NR1 immunoreactivity was significantly decreased, and was almost u ndetectable in this region until 12 h postietal: in contrast the NR2A/B imm unoreactivity in this region increased significantly in this time point. Th ese results suggest that the altering NMDA receptor expression in both the dentate gyrus and subiculum may affect tissue excitability and have an impo rtant role in regulating seizure activity in SS gerbils. (C) 2001 Elsevier Science B.V. All rights reserved.