Regulation of Mammalian Circadian Behavior by Non-rod, Non-cone, Ocular Photoreceptors

Science  16 Apr 1999:
Vol. 284, Issue 5413, pp. 502-504
DOI: 10.1126/science.284.5413.502

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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.

  • * Present address: School of Biological Sciences, University of Surrey, Guildford, Surrey GU2 5XH, UK.

  • To whom correspondence should be addressed. E-mail: r.foster{at}

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