Fine structure of experimental epileptogenic focus produced by intracerebral implantation of cobalt-gelatin stick in rabbits.

The experimental epileptogenic focus produced by cobalt-gelatin stick implantation in the cerebral cortex of rabbits has been studied by electron microscopy. Since our cobalt focus was latent, the bemegride maneuver was intravenously performed to identify the cobalt lesion of the cortex as an epileptogenic focus. The cobalt lesion comprised three different zones. Of the three zones, the reactive zone showed a glio-mesenchymal scar and prominent ultrastructural changes. The major change of this zone was found in the neurons, neuropils and astrocytes. Electron-lucent neurons deprived of the usual neuropils surrounding them, widening of extracellular spaces and swollen dendrites in neuropils, and proliferating astrocytes were observed constantly throughout the experimental period. These findings may be significant for the genesis of this type of epilepsy.