Melatonin induces Cry1 expression in the pars tuberalis of the rat

Brain Res Mol Brain Res. 2003 Jun 10;114(2):101-6. doi: 10.1016/s0169-328x(03)00134-7.


In mammals, interacting transcriptional/post-translational feedback loops involving 'clock genes' and their protein products control circadian organisation. These genes are not only expressed in the master circadian clock of the suprachiasmatic nuclei (SCN) but also in many peripheral tissues where they exhibit similar but not identical dynamic to that seen in the SCN. Among these peripheral tissues, the pars tuberalis (PT) of the pituitary expresses clock genes. We show here that the PT of the rat, like that of other rodents, rhythmically expresses Per1. We also report rhythmic expression of another clock gene, Cry1. The peak of Cry1 mRNA expression occurs during the night concomitantly with rising blood plasma melatonin concentrations. Using an acute injection paradigm, we demonstrate that Cry1 expression is directly induced by melatonin in the PT. Melatonin injection at the end of the subjective day also affects Per1 expression, leading to diminished mRNA levels. These data support the existence of a time-measurement model in the PT based on direct opposite actions of melatonin on Per1 and Cry1 expression.

MeSH terms

  • Animals
  • Biological Clocks / drug effects
  • Biological Clocks / genetics*
  • Cell Cycle Proteins
  • Circadian Rhythm / drug effects
  • Circadian Rhythm / physiology*
  • Cryptochromes
  • Drosophila Proteins*
  • Eye Proteins*
  • Flavoproteins / genetics*
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / genetics
  • Male
  • Melatonin / blood*
  • Melatonin / pharmacology
  • Nuclear Proteins / genetics
  • Period Circadian Proteins
  • Photoreceptor Cells, Invertebrate*
  • Pituitary Gland / cytology
  • Pituitary Gland / drug effects
  • Pituitary Gland / metabolism*
  • RNA, Messenger / drug effects
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Wistar / anatomy & histology
  • Rats, Wistar / metabolism*
  • Receptors, G-Protein-Coupled


  • Cell Cycle Proteins
  • Cry1 protein, rat
  • Cryptochromes
  • Drosophila Proteins
  • Eye Proteins
  • Flavoproteins
  • Nuclear Proteins
  • Per1 protein, rat
  • Period Circadian Proteins
  • RNA, Messenger
  • Receptors, G-Protein-Coupled
  • cry protein, Drosophila
  • Melatonin