Regulation of mammalian circadian behavior by non-rod, non-cone, ocular photoreceptors

Science. 1999 Apr 16;284(5413):502-4. doi: 10.1126/science.284.5413.502.


Circadian rhythms of mammals are entrained by light to follow the daily solar cycle (photoentrainment). To determine whether retinal rods and cones are required for this response, the effects of light on the regulation of circadian wheel-running behavior were examined in mice lacking these photoreceptors. Mice without cones (cl) or without both rods and cones (rdta/cl) showed unattenuated phase-shifting responses to light. Removal of the eyes abolishes this behavior. Thus, neither rods nor cones are required for photoentrainment, and the murine eye contains additional photoreceptors that regulate the circadian clock.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Clocks / physiology*
  • Circadian Rhythm / physiology*
  • Light*
  • Mice
  • Mice, Transgenic
  • Motor Activity
  • Ocular Physiological Phenomena*
  • Photoreceptor Cells, Vertebrate / physiology*
  • Pigments, Biological / physiology
  • Retinal Cone Photoreceptor Cells / physiology
  • Retinal Pigments / physiology
  • Retinal Rod Photoreceptor Cells / physiology


  • Pigments, Biological
  • Retinal Pigments