Diurnal rhythmic expression of the rhythm-related genes, rPeriod1, rPeriod2, and rClock, in the rat brain

Kun Ruey Shieh, Shu Chuan Yang, Xin Yun Lu, Huda Akil, Stanley J. Watson

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


High densities of the mRNA of three rhythm-related genes, rPeriod1 (rPer1), rPer2, and rClock, which share high homology in Drosophila and mammals, are found in the rat hypothalamic suprachiasmatic nucleus (SCN). The SCN, however, is not the only brain region that expresses these genes. To understand the possible physiological roles of these rhythm-related genes, we examined expression of these genes in different brain regions at various time points in male Sprague - Dawley rats. Using semi quantitativein situ hybridization with 35S-riboprobes to evaluate mRNA levels, the diurnal rhythmicity of rPer1, and rPer2 mRNA levels was found in the SCN, arcuate nucleus, and median eminence/pars tuberalis. Expression patterns of mRNA for rPer1 and rPer2, however, were not similar in these brain regions. The rhythmicity in these brain regions was specific, because it was not observed in the cerebellum or hippocampus. Moreover, diurnal changes in rClock mRNA expression were not detected in any of the brain regions examined. These findings suggest that the different expression patterns observed for rPer1, rPer2, and rClock mRNAs may be attributed to their different physiological roles in these brain regions, and support previous work indicating that circadian rhythms in the brain are widespread.

Original languageEnglish (US)
Pages (from-to)209-217
Number of pages9
JournalJournal of Biomedical Science
Issue number1
StatePublished - Jan 2005
Externally publishedYes


  • Arcuate nucleus
  • Cerebellum
  • Circadian rhythm
  • Hippocampus
  • Pars tuberalis/median eminence
  • Suprachiasmatic nucleus

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Pharmacology (medical)


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