title: Effects of nocturnal light on (clock) gene expression in peripheral organs: a role for the autonomic innervation of the liver.
abstract: BACKGROUND
  The biological clock, located in the hypothalamic suprachiasmatic nucleus (SCN), controls the daily rhythms in physiology and behavior. Early studies demonstrated that light exposure not only affects the phase of the SCN but also the functional activity of peripheral organs. More recently it was shown that the same light stimulus induces immediate changes in clock gene expression in the pineal and adrenal, suggesting a role of peripheral clocks in the organ-specific output. In the present study, we further investigated the immediate effect of nocturnal light exposure on clock genes and metabolism-related genes in different organs of the rat. In addition, we investigated the role of the autonomic nervous system as a possible output pathway of the SCN to modify the activity of the liver after light exposure.
  
  
  RESULTS
  First, we demonstrated that light, applied at different circadian times, affects clock gene expression in a different manner, depending on the time of day and the organ. However, the changes in clock gene expression did not correlate in a consistent manner with those of the output genes (i.e., genes involved in the functional output of an organ). Then, by selectively removing the autonomic innervation to the liver, we demonstrated that light affects liver gene expression not only via the hormonal pathway but also via the autonomic input.
  
  
  CONCLUSIONS
  Nocturnal light immediately affects peripheral clock gene expression but without a clear correlation with organ-specific output genes, raising the question whether the peripheral clock plays a "decisive" role in the immediate (functional) response of an organ to nocturnal light exposure. Interestingly, the autonomic innervation of the liver is essential to transmit the light information from the SCN, indicating that the autonomic nervous system is an important gateway for the SCN to cause an immediate resetting of peripheral physiology after phase-shift inducing light exposures.
authors.affiliation: Netherlands Institute for Neuroscience, Amsterdam, The Netherlands. c.cailotto@amc.uva.nl
authors.forename: Cathy
authors.initials: C
authors.lastname: Cailotto
authors.forename: Jun
authors.initials: J
authors.lastname: Lei
authors.forename: Jan
authors.initials: J
authors.lastname: van der Vliet
authors.forename: Caroline
authors.initials: C
authors.lastname: van Heijningen
authors.forename: Corbert G
authors.initials: CG
authors.lastname: van Eden
authors.forename: Andries
authors.initials: A
authors.lastname: Kalsbeek
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Ruud M
authors.initials: RM
authors.lastname: Buijs
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D017763:Autonomic Denervation; D001341:Autonomic Nervous System / Q000528:radiation effects*; D001683:Biological Clocks / Q000235:genetics* / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000235:genetics / Q000528:radiation effects; D003624:Darkness; D005786:Gene Expression Regulation / Q000528:radiation effects*; D006728:Hormones / Q000378:metabolism; D008099:Liver / Q000294:innervation* / Q000378:metabolism / Q000528:radiation effects; D008297:Male; D009928:Organ Specificity / Q000235:genetics* / Q000528:radiation effects; D010870:Pineal Gland / Q000378:metabolism / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D006728:Hormones