Blood—brain barrier permeability during electroshock seizures in the rat

Abstract

The effect of electrically induced seizures on the permeability of the rat blood-brain barrier was investigated. The small radioactive tracers 24Na+, 36Cl-, 14C-thiourea and 14C-D-glucose were studied in indicator dilution experiments with In labeled diethylenetriaminepentaacetic acid (113mIn-DTPA) as reference substance. This method allowed a quantative estimate of the transcapillary loss of solutes the extraction (E) during a single passage through the brain. Passage of macromolecules was studied using as marker substance Evans Blue which binds to plasma albumin. In the resting state ENa, ECl, Ethiourea and Eglucose were 2.9, 4.8, 9.3 and 12.5%, respectively. During seizures and shortlasting hypercapnia, E glucose decreased; E for the other tracers was unchanged. As cerebral blood flow increased, there must be an increased transfer of test substances into the brain. This agreed with recent human studies. When Evans Blue was injected i.v. prior to electroschock, there was no staining of brain tissue after 1 electroshock, but following repeated electroshocks some staining was observed. In an attempt to quantify this transcapillary loss of albumin by indicator dilution, 51Cr-labeled erythrocytes were used as intravascular reference substance against 113mIn-DTPA (a plasma tracer). The albumin loss (by pinocytosis or otherwise) occurring after 10 electroshocks could not be detected during a single passage through the brain.