Cerebral blood flow and metabolic rate during seizures. Relationship to epileptic brain damage

Abstract

After long periods of status epilepticus, selective neuronal necrosis is incurred in the neocortex (layer III-IV), in the hippocampus (CA1 and CA4), and in the thalamus (VPL-VPM). In these areas the cerebral metabolic rate for glucose is increased to between 200-300% of control, indicating a correlation between neuronal damage and enhanced neuronal activity. Measurements of local cerebral blood flow indicate that the damage is not due to insufficient supply of oxygen. In most rats with status epilepticus lasting longer than 30 minutes, an infarction develops in the substantia nigra pars reticulata. In this region the metabolic rate is first increased but later during the seizure activity falls to very low values indicating cell necrosis.

Conclusion: prolonged neuronal hyperactivity with a concomitant increase in the metabolic rate for glucose is a prerequisite for the development of neuronal damage. However, the necrosis of the SNPR demonstrates that other factors determine the vulnerability of neurons to hyperexcitation, e.g., the type of agonist acting on the neuron.