Circadian clock system in the pineal gland

Yoshitaka Fukada*, Toshiyuki Okano

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

68 Citations (Scopus)


The pineal gland is a neuroendocrine organ that functions as a central circadian oscillator in a variety of nonmammalian vertebrates. In many cases, the pineal gland retains photic input and endocrinal-output pathways both linked tightly to the oscillator. This contrasts well with the mammalian pineal gland equipped only with the output of melatonin production that is subject to neuronal regulation by central circadian oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Molecular studies on animal clock genes were performed first in Drosophila and later developed in rodents. More recently, clock genes such as Per, Cry, Clock, and Bmal have been found in a variety of vertebrate clock structures including the avian pineal gland. The profiles of the temporal change of the clock gene expression in the avian pineal gland are more similar to those in the mammalian SCN rather than to those in the mammalian pineal gland. Avian pineal gland and mammalian SCN seem to share a fundamental molecular framework of the clock oscillator composed of a transcription/translation-based autoregulatory feedback loop. The circadian time-keeping mechanism also requires several post-translational events, such as protein translocation and degradation processes, in which protein phosphorylation plays a very important role for the stable 24-h cycling of the oscillator and/or the photic-input pathway for entrainment of the clock.

Original languageEnglish
Pages (from-to)19-30
Number of pages12
JournalMolecular Neurobiology
Issue number1
Publication statusPublished - 2002
Externally publishedYes


  • Biological rhythm
  • Chicken
  • Circadian clock
  • Clock gene
  • MAP kinase
  • Melatonin
  • Photic input
  • Pineal gland
  • Suprachiasmatic nucleus

ASJC Scopus subject areas

  • Neurology
  • Cellular and Molecular Neuroscience


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