Acute hypertension causing blood-brain barrier breakdown during epileptic seizures

The influence of shortlasting (less than 1 min) epileptic seizures on the permeability to protein of the blood-brain barrier (BBB) was studied in rats. The protein tracer, horseradish peroxidase (HRP) was used as marker substance. Monitoring arterial blood pressure (BP) and electroencephalogramme (EEG) seizures were induced electrically after HRP was given intravenously. Following a single electroshock seizure slight staining of brain tissue was seen, while after 10 electroshock stimuli followed by sustained seizure activity, this phenomenon was more pronounced. If 10 electroshock stimuli were preceded by transsection of the spinal cord, blood pressure increase was abolished and no tissue staining was seen in spite of epileptic seizure activity recorded on EEG. This means that the acute hypertension and not the seizure activity per se is the mechanism behind the breakdown of the BBB during epileptic seizures. Electron microscopy revealed an increased vesicular transport (pinocytosis) across the endothelial cells, while the vascular structure remained intact.