N-acetyl aspartate estimation: a potential method for determining neuronal loss in the transmissible spongiform encephalopathies.

Neurodegenerative pathology is typical of the transmissible spongiform encephalopathies (TSEs), and is thought to underlie clinical disease. Some morphometric studies have shown early focal neurone loss, but the full extent of TSE induced neuronal loss in the central nervous system is not known, and can only be accurately estimated using intensive morphometric techniques. We have used a murine scrapie model in which we determined the levels of N-acetyl aspartate (NAA), a putative neuronal marker, by both high-performance liquid chromatography and high resolution, proton magnetic resonance spectroscopy in samples taken sequentially from the hippocampus. This scrapie model develops severe neuronal loss in the hippocampus, and the NAA levels showed a significant positive correlation with our previous morphometric estimates of neurone number. NAA measurement may therefore provide a practical alternative to intensive morphometric techniques in the investigation of neurodegeneration in the TSEs.