Regulation of tryptophan hydroxylase expression by a retinal circadian oscillator in vitro

Carla B. Green, Gregory M. Cahill, Joseph C. Besharse

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Many aspects of retinal physiology are controlled by a circadian clock including at least two steps in the melatonin synthetic pathway: the activity of the enzyme,N-acetyltransferase (NAT), and mRNA levels of the rate-limiting enzyme tryptophan hydroxylase (TPH). Light and dopamine (through D2-like dopamine receptors) can phase shift the clock, and can also acutely inhibit NAT activity, resulting in supressed melatonin synthesis. In this paper, we show that eyecups cultured in constant darkness maintain a clock-controlled rhythm in TPH mRNA, with low levels in early day, rising to a peak in early night. Both eyecups and isolated retinas, cultured in light during the day, also exhibit a similar increase in TPH mRNA levels, indicating that this expression is not acutely inhibited by light. Treatment with light or quinpirole (D2 dopamine receptor agonist) in early night, at a time and dose that acutely inhibits NAT activity, does not change levels of TPH mRNA. Addition of eticlopride (D2 dopamine receptor antagonist) during the day, also has no effect on the normal daytime increase in TPH message levels. Therefore, TPH mRNA level is controlled by a circadian clock located within the eye, but acute effects of light or dopamine are not detected.

Original languageEnglish (US)
Pages (from-to)283-290
Number of pages8
JournalBrain Research
Volume677
Issue number2
DOIs
StatePublished - Apr 24 1995

Fingerprint

Tryptophan Hydroxylase
Acetyltransferases
Light
Messenger RNA
Circadian Clocks
eticlopride
Melatonin
Dopamine
Quinpirole
Dopamine D2 Receptors
Darkness
Dopamine Agonists
Enzymes
Retina
In Vitro Techniques

Keywords

  • Circadian
  • Dopamine
  • Light
  • Melatonin
  • Retina
  • Serotonin
  • Tryptophan hydroxylase
  • Xenopus

ASJC Scopus subject areas

  • Developmental Biology
  • Molecular Biology
  • Clinical Neurology
  • Neuroscience(all)

Cite this

Regulation of tryptophan hydroxylase expression by a retinal circadian oscillator in vitro. / Green, Carla B.; Cahill, Gregory M.; Besharse, Joseph C.

In: Brain Research, Vol. 677, No. 2, 24.04.1995, p. 283-290.

Research output: Contribution to journalArticle

Green, Carla B. ; Cahill, Gregory M. ; Besharse, Joseph C. / Regulation of tryptophan hydroxylase expression by a retinal circadian oscillator in vitro. In: Brain Research. 1995 ; Vol. 677, No. 2. pp. 283-290.
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