Electrical and Vascular Concomitants of Spreading Depression

Abstract

Spreading depression is accompanied by a slow potential change, a drop in cortical conductivity and by vascular changes. The latter were investigated in histological preparations of cortex frozen while a spreading depression was in progress. In the cat and rabbit a broad wave of vasodilatation was observed. In the rabbit this appeared to be preceded by a narrow region of vasoconstriction. Spreading depression can be changed into spreading convulsive activity by administering CO₂ in the respiratory air (7–12%). CO₂ markedly decreased the drop in cortical conductivity but affected the magnitude of the slow potential change only moderately. It is postulated that both the conductivity drop during spreading depression and a similar drop observed after asphyxiation of the brain are caused by a transport of ions from the intercellular compartment into cortical cellular elements. The relationship between the slow potential change, conductivity drop, vascular changes and the changes in the electrocorticogram during spreading depression is discussed.