Daily rhythms in olfactory discrimination depend on clock genes but not the suprachiasmatic nucleus.
The suprachiasmatic nucleus (SCN) regulates a wide range of daily behaviors and has been described as the master circadian pacemaker. The role of daily rhythmicity in other tissues, however, is unknown. We hypothesized that circadian changes in olfactory discrimination depend on a genetic circadian oscillator outside the SCN. We developed an automated assay to monitor olfactory discrimination in individual mice throughout the day. We found olfactory sensitivity increased approximately 6-fold from a minimum during the day to a peak in the early night. This circadian rhythm was maintained in SCN-lesioned mice and mice deficient for the Npas2 gene but was lost in mice lacking Bmal1 or both Per1 and Per2 genes. We conclude that daily rhythms in olfactory sensitivity depend on the expression of canonical clock genes. Olfaction is, thus, the first circadian behavior that is not based on locomotor activity and does not require the SCN.
Department of Biology, Washington University, St. Louis, MO 63130-4899, USA. dgranado@biology2.wustl.edu
Daniel
D
Granados-Fuentes
Gal
G
Ben-Josef
Gavin
G
Perry
Donald A
DA
Wilson
Alexander
A
Sullivan-Wilson
Erik D
ED
Herzog
D056930:ARNTL Transcription Factors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001683:Biological Clocks / Q000502:physiology; D056926:CLOCK Proteins / Q000235:genetics* / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D012903:Smell / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000473:pathology / Q000502:physiology*
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D009419:Nerve Tissue Proteins; C538961:Bmal1 protein, mouse; C491259:Npas2 protein, mouse