Bicuculline-induced epileptic brain injury. Transient and persistent cell changes in rat cerebral cortex in the early recovery period.

It was earlier shown that bicuculline-induced status epilepticus gives rise to profound acute changes in the rat cerebral cortex, i.e. edema and neuronal alterations. In the present study, we explored to what extent interruption of the seizure activity reverses the changes observed. To that end, status epilepticus of 1 and 2h duration was induced by bicuculline before the seizures were arrested by i.v. injection of diazepam. The brain was then fixed by vascular perfusion either 5 min (1 h of seizures) or 2h (1 and 2h of seizures) of recovery and cerebral cortical tissue was studied by light (LM) and electron microscopy (EM). Already 5 min following the arrest of seizure activity most of the astrocytic edema had disappeared, and the 2h of recovery, following 1 h of status epilepticus, the edema was virtually absent, and only few injured cells were found (only about 1% of the neuronal population). When recovery was instituted after 2 h of status epilepticus, numerous dark, triangular neurons were found. In the last group an adequate blood pressure could not be obtained. Therefore, the cellular alterations observed were probably not the result of the seizure activity per se. After 5 min of recovery, Em studies showed condensed, dark-staining injured neurons, similar to those previously observed in non-recovery animals. However, an increased incidence of swollen mitochondria was observed. After 2 h of recovery a few severely injured neurons remained which showed signs of progressive injury with fragmentation of the cell body.