Rat photoreceptor circadian oscillator strongly relies on lighting conditions

Clock genes in rat photoreceptors display rhythmic expression in a 24-hour light-dark cycle.

• Clock, Bmal1, Per1, Per2, Cry1, Cry2, RevErbα, and Rorβ clock genes are all expressed in rat photoreceptors.
• Rhythmic transcription of clock genes is observed in photoreceptors when exposed to a light-dark cycle.
• Similar rhythmic expression profiles of clock genes are found in whole retinas compared to isolated photoreceptors.
• After 36 hours of constant darkness, oscillations of most clock genes in photoreceptors are no longer detectable.
• Two clock output genes, Aanat and c-fos, maintain rhythmicity even in constant darkness.
• The findings suggest that photoreceptors have a functional circadian oscillator that relies on light exposure.

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