EXTRACELLULAR AMINO-ACIDS IN THE RAT HIPPOCAMPUS DURING PICROTOXIN THRESHOLD SEIZURES IN CHRONIC MICRODIALYSIS EXPERIMENTS

The relation between changes in the concentrations of some of the neur oactive extracellular amino acids (glutamate, aspartate, gamma-aminobu tyric acid, glycine and taurine) and epileptic seizures has been teste d in a new experimental model of seizures induced by picrotoxin microd ialysis in chronic freely moving rats. During ictal discharges (paroxy smal electroencephalographic discharges associated with behavioral sei zures), a significant decrease in the levels of extracellular aspartat e and glutamate was observed. However, no changes were found during th e interictal discharges (paroxysmal electroencephalographic discharges , without concomitant seizures). Our results suggest that modification s in extracellular aspartate and glutamate may be related to neuronal synchronization rather than to paroxysmal activity, supporting the neu rophysiological differences between non-ictal and ictal paroxysmal act ivity. (C) 1998 Elsevier Science Ireland Ltd.