Entorhinal cortex lesion studied with the novel dye Fluoro-Jade

We used the fluorescent dye Fluoro-Jade, capable of selectively staining de generating neurons and their processes, in order to analyze degenerative ef fects of transecting the hippocampus from its main input, the entorhinal co rtex in vivo and in organotypical hippocampal slice culture. Degenerating f ibers stained with Fluoro-Jade were present as early as 1 day postlesion in the outer molecular layer of the dentate gyrus and could be detected up to 30 days postlesion. However, the intensity of the Fluoro-Jade staining in the outer molecular layer faded from postlesional day 20 onward. Punctate s taining, various cells and neural processes became visible in this area sug gesting that degenerating processes were phagocytosed by microglial cells o r astrocytes. We conclude that Fluoro-Jade is an early and sensitive marker for studying degenerating neurites in the hippocampal system. (C) 2000 Els evier Science B.V. All rights reserved.