Postmortal diffusion of plasma albumin in rat brain.

After i.v. injection of Evans blue solution (EB), the postmortal diffusion of plasma albumin and its relationship to the postmortal interval (0 to 48 h) were studied in rat brain. A decrease in intravascular plasma albumin with increasing evidence of the same fraction in relation to the length of the postmortal interval was observed via diffuse EB fluorescence in the perivascular, periventricular, and subpial neuropil. Stained nerve cells and single endothelial cells were found grouped around individual vessels, particularly in the region of the basis encephali. The EB-fluorescent cells proved to be hyperchromatic when subsequently stained with cresyl violet; the nerve cells therefore were considered dark neurons. EB-fluorescent dark neurons were also found around the lesion in experiments involving postmortal traumatic damage of cerebral tissue. Since all EB-fluorescent nerve cells proved to the dark neurons, but not all dark neurons exhibited EB fluorescence, it was concluded that dark neurons possess a capacity for intensifying the absorption of plasma albumin. No fluorescence was demonstrated in control studies of cerebral tissue in which EB had not been injected.