Intramembranous cytochemistry: a new morphological technique for studying cholesterol in the astrocyte plasma membrane of ischemic brain cells

The distribution of cholesterol in the astrocytic plasma membranes of normal and ischemic caudate nucleus in the cat was investigated with the polyene antibiotic, filipin, a morphological probe for membrane cholesterol domains in freeze-fracture tissue replicas. After filipin incubation of prefixed vibratome slices, filipin-cholesterol complexes appeared as 20 to 30 nm protuberances and pits on P- and E-faces of the replicas. Distinct patterns of filipin-cholesterol complexes were found on nonischemic and ischemic astrocyte membranes. The filipin-treated specimens showed an 80% decrease in astroglial plasmalemma of cholesterol 1 hour after cerebral ischemia.