Daily variations of blood glucose, acid-base state and PCO2 in rats: Effect of light exposure

Etienne Challet*, André Malan, Fred W. Turek, Olivier Van Reeth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The suprachiasmatic nuclei (SCN) of the hypothalamus are the site of the main circadian clock in mammals. Synchronization of the SCN to light is achieved by direct retinal inputs. The present study performed in rats transferred to constant darkness shows that blood glucose, pH and PCO 2 display significant diurnal changes when measurements were made during the subjective day, the early subjective night or the late subjective night. The effects of a 30-min light exposure (100 lx) on these metabolic parameters at each of these circadian times were assessed. Regardless of the circadian time, light induced an increase in blood glucose, but did not affect plasma pH and PCO2. This study suggests that blood glucose, PCO 2 and acid-base state are under circadian control, most likely mediated by the SCN, while the hyperglycemic response to light seems not to be gated by a circadian clock and may thus involve retinal inputs to non-SCN retino-recipient areas.

Original languageEnglish (US)
Pages (from-to)131-135
Number of pages5
JournalNeuroscience Letters
Issue number1-2
StatePublished - Jan 23 2004


  • Blood glucose
  • Blood pH
  • Circadian rhythm
  • Suprachiasmatic nucleus

ASJC Scopus subject areas

  • Neuroscience(all)


Dive into the research topics of 'Daily variations of blood glucose, acid-base state and PCO2 in rats: Effect of light exposure'. Together they form a unique fingerprint.

Cite this