[Retrogression of the metabolic activity of astrocytes after extinction of an experimental epileptogenic focus. Histochemical investigation]

Abstract

Previous anatomochemical and experimental investigations had resulted in the histochemical characterisation of the epileptogenic focus by the presence of "activated astrocytes"; cortical reactive astrocytes acquiring an intense activity of sundry dehydrogenases (DH) and becoming visible in spite of the positivity of the neuropil, and stopping at the amylose step in the synthesis of glycogen. This activation exists from the first electrical sings of epilepsy and even preceeds them in the case of glucose-6-phosphate DH. The present study deals with the fate of activated astrocytes after the disappearance of electrical signs of the epileptogenic focus produced by implantation of a cobalt powder-gelatin pellet into the cerebral cortex of the rat. After extinction of the focus, high activity of DH persists in astrocytes only in the immediate vicinity of the glial scar surrounding the implant. Later, among the DH investigated only glutamate and specially glucose-6-phosphate DH maintain an activity intense enough to reveal these cells on the background of the neuropil. These results point to a progressive return to a normal metabolism of astrocytes after the disappearance of the electrical signs of epilepsy by way of steps similar to those preceeding these signs.