EDITING STATUS AT THE Q R-SITE OF GLUTAMATE RECEPTOR A-SUBUNIT, B-SUBUNIT, 5-SUBUNIT AND 6-SUBUNIT MESSENGER-RNA IN THE HIPPOCAMPAL KINDLING MODEL OF EPILEPSY/

The editing status of mRNA at the Q/R site of the glutamate receptor s ubtypes -A, -B, -5 and -6 modulates channel conductivity and ion selec tivity of glutamate operated ion channels [4,15,26,30]. In order to in vestigate whether a modification of this editing process may be involv ed in kindling epileptogenesis, the percentage of edited variant was d etermined in the hippocampus of kindled rats and compared to the perce ntage in control animals. In the latter, GluR-A mRNA was detected only in the unedited form (with detection threshold for edited form < 0.7% ), whereas GluR-B was completely edited (> 99%). For GluR-5, the mean edited fraction of transcripts was in controls 36% and for GluR-6 the edited fraction was 92%. These editing percentages were not significan tly changed in Schaffer collateral/commissural pathway kindled animals that were sacrificed 24 h after the last generalized seizure. It is c oncluded that the increased sensitivity for the induction of seizures characteristic for Schaffer collateral kindled animals is not related to a less selective or less efficient mRNA editing process of the diff erent glutamate receptor subunits in the hippocampus.