Electron microscopic alterations in the vicinity of epileptogenic cobalt-gelatine necrosis in the cerebral cortex of the rat

In 25 adult rats an epileptogenic cobalt-gelatine focus was produced in a standard region of the cerebral cortex. The animals were killed successively on the 1st, 3rd, 5th, 8th, 14th, 21st and 28th day after operation and the region of the epileptogenic focus was examined electron microscopically. The earliest changes were those of oedema. Later there occurred disturbances of the astrocytic processes which cling to the basement membranes of the capillaries; the intercellular spaces widened and filled with rather E. M. dense masses and a “plasmatic infiltrate” developed. Gradually this exudative substance spread even further from the capillaries. It appeared in places where the astrocytic processes were severely demaged and the dendrites were partly dissipated and it filled out the wide intercellular spaces of the neuropil. The nerve cells showed a striking resistance toward this pathological process. Sometimes they floated in the exudative masses but were partly or totally deprived of the fine neural and astrocytic processes which normally surround them. Our findings are interpreted as the ultrastructural correlate of Scholz's “plasmatic infiltration”.