The permeability of the blood—brain barrier during electrically induced seizures in man

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Abstract
The blood-brain barrier (BBB) in man was studied during various conditions using the indicator dilution method of Crone. Using 113mIn-DTPA [diethylenetriaminepentaacetic acid] as reference substance, the extraction, E, of the small test substances 24Na+, 36Cl-, 14C-urea and 14C-thiourea was estimated from the areas under the venous outflow curves followng intracarotid slug injection of tracers. Interlaminar diffusion and red cell carriage were taken into consideration when calculating E. Cerebral blood flow (CBF) was measured using the intra-arterial 133Xe injection method. Patients (22) receiving electroconvulsive therapy (ECT) were studied before and during seizures and during hypercapnia. Before seizures the extraction values in percent were as follows: ENa+ 1.6, ECl- 1.9, Eurea 3.9 and Ethiourea 7.8; the coresponding values for the permeability-surface area products (PS) in ml/100 g .times. min were 0.5, 0.3, 0.7 and 4.1, respectively. During seizure a decrease of Ethiourea and an increase of PSurea were significant. During hypercapnia PSNa and PSthiourea rose significantly. Due to the similarity of the findings in those 2 high flow situations it was suggested that the changes of CBF and not the epileptic activity are responsible for the changes in permeability. The mechanism of action may be a stretching of endothelial cells in the cerebral vessels, an opening up of new capillaries or a combination of both.