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Updated: Jul 16, 2026

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
Published on: November 11, 2016
Regulation of mammalian circadian behavior by non-rod, non-cone, ocular photoreceptors
M S Freedman1, R J Lucas, B Soni
1Department of Biology, Alexander Fleming Building, Imperial College of Science, Technology and Medicine, London, SW7 2AZ, UK.
Abstract:
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.
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