Circadian rhythms in mice can be regulated by photoreceptors with cone-like characteristics.
In this report we have characterized the photopigments mediating circadian phase shifts in retinal degenerate (rd) mice. In aged rd/rd mice, which lack detectable opsin, high performance liquid chromatography (HPLC) was used to quantify the photopigment chromophore 11-cis-retinaldehyde. This chromophore was photoisomerized in whole eyes, suggesting the presence of a functional opsin-based photopigment system. We also analyzed the spectral sensitivity of phase shifting circadian locomotor rhythms. Our data implicate a photopigment that is consistent with the involvement of the middle wavelength-sensitive cone photoreceptors (M-cones; lambda(max) = 511 nm) found in the mouse retina. In addition, discrete near-ultraviolet (UV-A) pulses were capable of eliciting large phase shifts in circadian locomotor activity rhythms. This result is consistent with the involvement of the short wavelength-sensitive cone photoreceptors (UV-cones; lambda(max) = 359 nm) in photoentrainment. Collectively, these data suggest that both cone classes of the mouse may mediate the photic regulation of circadian rhythms. If this is the case, circadian sensitivity can be maintained by very few degenerate cones. Alternatively, an unknown class of ocular photoreceptor may fulfill this function.
Provencio
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Department of Biology, University of Virginia, Charlottesville 22903, USA.
Foster
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D000818:Animals; D001522:Behavior, Animal; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm; D005123:Eye / Q000378:metabolism; D007536:Isomerism; D008027:Light; D051379:Mice; D008810:Mice, Inbred C57BL; D010786:Photoreceptor Cells / Q000502:physiology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology; D012176:Retinoids / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays
D012176:Retinoids