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Role of melanopsin in circadian responses to light.

Melanopsin has been proposed as an important photoreceptive molecule for the mammalian circadian system. Its importance in this role was tested in melanopsin knockout mice. These mice entrained to a light/dark cycle, phase-shifted after a light pulse, and increased circadian period when light intensity increased. Induction of the immediate-early gene c-fos was observed after a nighttime light pulse in both wild-type and knockout mice. However, the magnitude of these behavioral responses in knockout mice was 40% lower than in wild-type mice. Although melanopsin is not essential for the circadian clock to receive photic input, it contributes significantly to the magnitude of photic responses.

Pubmed ID: 12481140


  • Ruby NF
  • Brennan TJ
  • Xie X
  • Cao V
  • Franken P
  • Heller HC
  • O'Hara BF


Science (New York, N.Y.)

Publication Data

December 13, 2002

Associated Grants

  • Agency: NIDA NIH HHS, Id: DA13349
  • Agency: NHLBI NIH HHS, Id: HL64148
  • Agency: NIMH NIH HHS, Id: MH60385

Mesh Terms

  • Animals
  • Biological Clocks
  • Circadian Rhythm
  • Darkness
  • Female
  • Gene Expression Regulation
  • Gene Targeting
  • Genes, fos
  • In Situ Hybridization
  • Light
  • Light Signal Transduction
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Motor Activity
  • Retinal Ganglion Cells
  • Rod Opsins
  • Suprachiasmatic Nucleus