N-METHYL-D-ASPARTATE AND KAINATE RECEPTOR GENE-EXPRESSION IN HIPPOCAMPAL PYRAMIDAL AND GRANULAR NEURONS IN THE KINDLING MODEL OF EPILEPTOGENESIS

To investigate the changes underlying kindling epileptogenesis in the rat hippocampus, the levels of the messenger RNAs encoding for the sub units of the N-,methyl-D-aspartate-receptor (1, 2A-D) and the kainate- receptor (1, -2, GluR-5, -6, -7) were determined in hippocampal princi pal neurons using in situ hybridization techniques and semi-quantitati ve analysis of the autoradiograms. Schaffer collateral-commissural pat hway kindled rats were investigated at three differant stages of kindl ing acquisition, always 24 h after the last stimulation. Furthermore, fully kindled rats were studied at long-term (28 days) after terminati on of kindling stimulations. NR1 messenger RNA levels were slightly de creased in CA1 area of fully kindled animals. In the fascia dentata re gion, a minor increase of NR2A and NR2B transcripts was found at all s tages of kindling acquisition. KA-2 messenger RNA was enhanced in all hippocampal subfields during kindling development. However, none of th ese changes persisted at long-term after the last seizure and only the low-abundant GluR-7 expression was slightly depressed in the fascia d entata. From our observations we conclude that it is unlikely that alt erations in N-methyl-Daspartate or kainate receptor gene expression pl ay an important role in kindling acquisition or maintenance.