Modulation of Retinal Aromatic l‐Amino Acid Decarboxylase via α2 Adrenoceptors

Zvani Rossetti, Dimitrij Krajnc, Norton H. Neff*, Maria Hadjiconstantinou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Abstract: Aromatic l‐amino acid decarboxylase (AAAD) activity of the rat retina increases when animals are placed in a lighted environment from the dark. The rise of activity can be inhibited by administering α2 adrenoceptor agonists. In the dark, the enzyme activity can be made to increase by administering α2 adrenoceptor antagonist drugs. Kinetic analysis indicates that the maximum velocity of the enzyme increases with little change of the Km for the substrate l‐3,4‐dihydroxyphenylalanine or the cofactor pyridoxal‐5′‐phosphate. The rise of activity in the light and in the dark after α2 antagonists can be blocked by administering cycloheximide, suggesting that protein synthesis is needed for the response. We speculate that epinephrine released in the dark from a subpopulation of retinal amacrine cells onto α2 receptors suppresses AAAD activity that is associated with dopaminergic amacrines.

Original languageEnglish (US)
Pages (from-to)647-652
Number of pages6
JournalJournal of neurochemistry
Issue number2
StatePublished - Feb 1989


  • Aromatic l‐amino acid decarboxylase
  • Catecholamines
  • Dopamine
  • Epinephrine
  • Retina
  • α adrenoceptors

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience


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