[Amino acid metabolism in neurodegenerative diseases]

Although various neurological diseases occur in patients with inborn error of metabolism of amino acids, amino acids also act as neurotransmitters. Glutamic acid, aspartic acid and glycine play roles as an excitatory neurotransmitter, but exert a neurodegenerative effect in case of the excessive release. Extensive studies have recently been performed on glutamate receptors, especially N-methyl-D-aspartate (NMDA) receptor in the hippocampus. Alzheimer brain shows a decreased number of NMDA receptors in the frontal cortex. The parkinsonian changes caused by MPTP is abolished by the administration of a NMDA antagonist. gamma-Aminobutyric acid (GABA) acts as an inhibitory amino acid. The content of GABA is low in the striatum of patients with Huntington's disease. The number of NMDA receptor is decreased also in Huntington striatum. These observations may give a clue for the prevention of various neurodegenerative diseases.