Blood—brain barrier permeability during electroshock seizures in the rat

Abstract

Abstract. The effect of electrically induced seizures on the permeability of the rat blood-brain barrier was investigated. The small radioactive tracers sodium (²⁴N⁺), chloride (³⁶Cl^-), carbon labelled thiourea (¹⁴C-thiourea) and glucose (¹⁴C-D-glucose) were studied in indicator dilution experiments with indium labelled diethylene-triaminepenta-acetic acid (^113mIn-DTPA) as reference substance. This method allows a quantitative 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 E_Na, E_Cl, E_thiourea and E_glucose were 2.9, 4.8, 9.3 and 12.5%, respectively. During seizures and during shortlasting hypercapnia E glucose decreased while 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 finding is in agreement with recent human studies [15]. When Evans Blue was injected intravenously prior to electroshock, there was no staining of brain tissue after one electroshock but following repeated electroshocks some staining was observed. In an attempt quantify this transcapillary loss of albumin by means of indicator dilution, ⁵¹Cr-labelled erythrocytes were used as intravascular reference substance against ^113mIn-DTPA (a plasma tracer). However, the albumin loss (by pinocytosis or otherwise) occurring after ten electroshocks could not be detected during a single passage through the brain.