Tryptophan Metabolites in Parkinson’s Brain
Quinolinic acid (QA) is an intermediate in the kynurenic pathway from tryptophan (TRP) to nicotinic acid. Recently, QA has been demonstrated to be increased in the aging rat brain1 and to act on neurons as an endogenous excitotoxin.2 Kynurenic acid (KYA), another product of this pathway, has been shown to antagonize excitotoxic amino acids and QA.3 Based on these findings, it has been proposed that changes in the balance between QA and KYA are related to the pathogenesis of several neurodegenerative disorders.4 Indeed, Schwarcz et a1.2 reported that QA produced striatal lesions similar to those of Huntington’s disease, and Beal et al.5 also found the formation of KYA was reduced in Huntington’s striatum, whereas Moroni et al.6 failed to find any increase in QA in Alzheimer’s cortex.
KeywordsSubstantia Nigra Kainic Acid Quinolinic Acid Kynurenic Acid Striatal Lesion
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