Extracellular amino acid levels measured with intracerebral microdialysis in the model of posttraumatic epilepsy induced by intracortical iron injection

An iron induced model of posttraumatic chronic focal epilepsy in rats was s tudied with respect to extracellular amino acids, electrophysiology, and mo rphology, approx. 6 months after intracortical injection of ferrous chlorid e. Twenty-six of the twenty-eight (93%) rats developed spontaneous epilepti form EEG-activity and electrical cortical stimulation done in eight animals evoked seizure activity in five animals (62.5%). Epileptic brain tissue di splayed significantly higher extracellular interictal levels of aspartate ( ASP), compared to normal brain, measured with intracerebral microdialysis. The interictal levels of serine (SER) were significantly higher at the lesi on side compared to the contralateral cortex in epileptic animals. Spontane ous elevations of ASP and glutamate (GLU) levels up to 8 times the basal le vel were found in 4/5 (80%). There was no consistent amino acid pattern fol lowing the electrically induced seizures, but in association with more inte nse seizure activity ASP and GLU were elevated. Histopathologically, the ne crotic lesions in the cortex contained small vessels and iron pigment loade d astrocytes. Scattered eosinophilic neurons were found in the hippocampus, bilaterally in 37% of the animals. The results show that a focal epileptif orm activity developed in a high percentage of animals that received an int racortical iron injection. The observed amino acid changes in epileptic ani mals may be involved in the development of seizures in this model of posttr aumatic epilepsy. (C) 2001 Elsevier Science B.V. All rights reserved.