Neurone-specific enolase persists in some hippocampal cells 24 hours after an NMDA injection

Neurone-specific enolase immunoreactivity (NSE-IR) was examined in the hippocampal dentate gyrus 5 h, 24 h and 6 days following local injection of N-methyl-D-aspartate (NMDA), and was compared with Nissl substance and acid fuchsin staining. Five and 24 hours post-injection extracellular NSE-IR was increased, and the number of NSE-IR neurones in the granule cell layer was decreased. However, at 24 h post-injection only, 10-15% of the granule cells were strongly NSE-IR, in contrast to the Nissl/acid fuchsin staining which showed a homogeneous population of degenerating neurones. By 6 days there were no viable neurones in the lesion area stained by either method. These results show that neuronal degeneration after an excitotoxic insult occurs in a non-uniform way in an apparently homogeneous group of central neurones.