Monosodium glutamate: increased neurotoxicity after removal of neuronal re-uptake sites.

Microinjections of monosodium glutamate (MSG; 300 microgram/0.5 microliter) into the hippocampus of the adult rat result in only marginal damage to local neurons. Perforant path transections, removing glutamatergic afferents to hippocampal granule cells, make the latter markedly more vulnerable to a subsequent MSG injection. The principle of modulating toxic effects of MSG by interfering with its neurotransmitter role may have significant impact on our understanding of human neurodegenerative disorders.