Striatal L‐DOPA Decarboxylase Activity in Parkinson's Disease In Vivo: Implications for the Regulation of Dopamine Synthesis

Albert Gjedde, Gabriel C. Léger, Paul Cumming, Yoshifumi Yasuhara, Alan C. Evans, Mark Guttman, Hiroto Kuwabara

Research output: Contribution to journalArticlepeer-review

Abstract

Abstract: L‐DOPA is a large neutral amino acid subject to transport out of, as well as into, brain tissue. Competition between dopamine synthesis and L‐DOPA egress from striatum must favor L‐DOPA egress if decarboxylation declines relatively more than transport in Parkinson's disease. To test this hypothesis, we injected patients with Parkinson's disease with a radidabeled analogue of L‐DOPA and recorded regional brain radioactivity as a function of time by means of positron emission tomography. We simultaneously estimated the activity of the decarboxylating enzyme and the amino acid transport. In the striatum of patients, we found the L‐DOPA decarboxylase activity to be reduced in the head of the caudate nucleus and the putamen. However, the rate of egress of the DOPA analogue was unaffected by the disease and thus inhibited dopamine synthesis more than predicted in the absence of L‐DOPA egress.

Original languageEnglish (US)
Pages (from-to)1538-1541
Number of pages4
JournalJournal of Neurochemistry
Volume61
Issue number4
DOIs
StatePublished - Oct 1993

Keywords

  • Dopamine synthesis
  • L‐DOPA
  • L‐DOPA decarboxylase
  • Parkinson's disease
  • Striatum

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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