Distribution of Exudated FITC-dextrans in Experimental Vasogenic Brain Edema Produced by a Focal Cryogenic Injury

Mice were subjected to cortical cryogenic brain injury, and FITC-dextrans (mol. wt. 20,000 or 150,000) were injected intravenously (i.v.). After a survival period of 4 h the distribution of the FITC-dextrans was determined by a histotechnical procedure described recently ( Hultstr öm et al. 1982a ). This technique is based on freeze-drying and vapor fixation to immobilize the tracer and to provide tissue fixation. In and around the cryogenic injury both tracers leaked out of the cortical and the leptomeningeal vessels and spread into the brain parenchyma. They were seen as multiple, closely apposed droplets of fluorescent material best recognized by fluorescence microscopy under high magnification. The tracers were also taken up by neuronal perikarya and in glial cell nuclei of, presumably, astrocytic origin. Our study shows that the FITC-dextran technique can be used for experimental studies on the vasogenic form of brain edema. The patterns formed by the extravasated tracers have qualitative similarities to those produced by other more commonly used tracers, such as fluorochrome-labeled serum proteins and peroxidase.