Nocturnal expression of phosphorylated-ERK1/2 in gastrin-releasing peptide neurons of the rat suprachiasmatic nucleus

J Neurochem. 2007 Jun;101(5):1224-35. doi: 10.1111/j.1471-4159.2006.04416.x. Epub 2007 Jan 22.


Extracellular regulated kinase (ERK) signalling is believed to play roles in various aspects of circadian clock mechanisms. In this study, we show in rat that the nuclear versus cytoplasmic intracellular distribution of the phosphorylated forms of ERK1/2 (P-ERK1/2) in the central clock, namely the suprachiasmatic nucleus (SCN), is proportionally constant across the light/dark cycle while the spatial distribution and neurochemical phenotype of cells expressing these activated forms are time-regulated according to a daily rhythm and light-regulated. P-ERK1/2 was exclusively found in neuronal elements. At daytime, it was detected throughout the dorsoventral extent of the SCN, partly within neurons synthesizing either arginine-vasopressin or vasoactive intestinal peptide (VIP). At night time, it was segregated in the ventrolateral aspect of the nucleus, within a cluster of cells 45% of which were gastrin-releasing peptide (GRP) neurons with or without co-localization with VIP. After a light pulse at night, expression of P-ERK1/2 increased in GRP neurons but also appeared in a population of neurons that stained for VIP only. These data show that the GRP neurons are closely associated with ERK1/2 activation at night and point to the importance of ERK1/2 signalling not only in intra-SCN transmission of photic information but also in maintenance of neuronal rhythms in the SCN.

MeSH terms

  • Animals
  • Arginine Vasopressin / metabolism
  • Cell Nucleus / metabolism
  • Circadian Rhythm / physiology*
  • Cytoplasm / metabolism
  • Gastrin-Releasing Peptide / metabolism*
  • Gene Expression Regulation / physiology*
  • Glial Fibrillary Acidic Protein / metabolism
  • Light
  • Male
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Neurons / classification
  • Neurons / cytology
  • Neurons / metabolism*
  • Phosphorylation
  • Rats
  • Rats, Sprague-Dawley
  • Suprachiasmatic Nucleus / cytology*
  • Vasoactive Intestinal Peptide / metabolism


  • Glial Fibrillary Acidic Protein
  • Arginine Vasopressin
  • Vasoactive Intestinal Peptide
  • Gastrin-Releasing Peptide
  • Mitogen-Activated Protein Kinase 3