Fine Structure of Experimental Epileptogenic Focus Produced by Intracerebral Implantation of Cobalt-Gelatine Stick in Rabbits

Abstract

The experimental epileptogenic focus produced by cobalt-gelatine 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.

Response of rat cerebral cortical astrocytes to freeze‐ or cobalt‐induced injury: An immunocytochemical and gap‐FRAP study

“…Astrocytic proliferation has been observed within and surrounding cerebral cortical lesions induced by cobalt (Brotchi et al, 1978;Nakamura et al, 1981;Payan, 1971). However, this is the first report to investigate the development, spread, and regression of increased astrocytic GFAP immunoreactivity throughout the entire cobalt-injured rat cerebral cortex.…”

“…A number of methods have been used to injure the cerebral cortex, including stab wounds (Bignami and Dahl, 1976;Billingsley et al, 1982;Fog and Pakkenberg, 1983;Latov et al, 1979;Mathewson and Berry, 1985) freeze injury (Amaducci et al, 1981;Hass and Taylor, 1953;Klatzo et al, 19581, and cobalt (Brotchi et al, 1978;Butler et al, 1976;Dodd et al, 1980;Nakamura et al, 1981;Payan, 1971). These methods were used to investigate the response of cells within the cerebral cortex to injury.…”

“…Besides describing the astrocytic reactivity within and surrounding the lesion, several of these reports dealt with the development of astrocytic reactivity throughout the injured cerebral cortex. Astrocyte response in the immediate vicinity of the lesion has been examined at the light microscopic and ultrastructural level after cobaltinduced injury (Brotchi et al, 1978;Butler et al, 1976;Nakamura et al, 1981;Payan, 1971) and freeze injury (Blakemore, 1971;Klatzo et al, 1958). However, the temporal and spatial distribution of astrocytic reactivity throughout the rat cerebral cortex, using GFAP immunolabeling, has not been examined after cobaltinduced injury and has been examined after freezeinjury in only one report (Amaducci et al, 1981).…”