N-acetylaspartylglutamate: an endogenous peptide with high affinity for a brain "glutamate" receptor.

A brain peptide with high affinity (420 nM) and marked specificity for brain receptor sites labeled with L-[3H]glutamate has been identified. Amino acid analysis and mass spectroscopy indicate that the peptide is N-acetylaspartylglutamate. The peptide exhibits potent convulsant properties when injected into the rat hippocampus, similar to those produced by the glutamate receptor agonist, quisqualic acid. These findings raise the question whether endogenous brain peptides enriched in acidic amino acids may serve as excitatory neurotransmitters.