Substantial evidence indicates that neuroactive kynurenine metabolites play a role in the normal physiology of the human brain, and are involved in the pathology of neurodegenerative disorders such as Parkinsons disease and Huntingtons disease. A side-arm product of the pathway, kynurenic acid (KYNA), which is synthesized by the irreversible transamination of kynurenine (KYN) by kynurenine aminotransferases (KAT I and KAT II), is an excitatory amino acid receptor antagonist. In the present study, we measured the level of KYNA and the activities of the biosynthetic enzyme isoforms KAT I and KAT II in the plasma and in the erythrocytes (RBCs) of patients with cervical dystonia or blepharospasm and in age-matched controls. The KAT I and KAT II activities were significantly lower in the plasma of the patients in both subgroups. In the RBCs, only the KAT I activity was elevated significantly. The KYNA concentration was unchanged in both type of patients. These data support the contribution of an altered kynurenine metabolism to the pathogenesis of focal dystonia.
Keywords: Cervical dystonia, blepharospasm, kynurenine aminotransferase, kynurenic acid, excitotoxicity
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