Time study of macroscopic identification of experimental cerebral infarction in rat

Cerebral infarctions were induced in rats by injection of Sephadex G-200 into the internal carotid artery. Unfixed slices of brain were stained with nitro blue tetrazolium (nitro-BT). Tissue dehydrogenase in normal regions reacts with this chemical and changes from a pale yellow color to dark blue consequent to formation of formazan. However, the color changes do not develop in infarcted tissue as there is depletion of tissue dehydrogenase in these regions. Ischemic lesions are identifiable by this method in over half the brain 2 to 4 hours after the embolization, but are seen in all brains 6 hours or more following the embolization. The procedure is simple, requires 30 minutes, and is useful for identification of small or acute cerebral infarction.