1993 · 66 citations · 0 references
NursingNeurobiologyNeuroscienceCircadian RhythmsGene ExpressionMolecular NeuroscienceCircadian Clock MechanismsCircadian Gene ExpressionCircadian Molecular MechanismsLight PerceptionPhotoreceptor PhysiologySuprachiasmatic NucleusCircadian BehaviorCone Opsin GenesGene Regulation In PhotoreceptorsHereditary Retinal DiseasePhotoreceptor BiologyRetinal PhotoreceptionSuprachiasmatic Nucleus ClockworkVisual Function Loss
Our recent studies have examined circadian photoreception in mice with hereditary retinal disorders (rd/rd and rds/rds). Despite the loss of visual function in these mice, circadian responses to light remain unaffected. Using c-fos expression within the suprachiasmatic nuclei (SCN) as a marker of neural activation of the circadian entrainment pathway, we have found identical levels of Fos in the SCN of rd/rd and +/+ mice in response to retinal illumination. On the basis of action spectrum studies, and measurements of photopigment retinoids using high-pressure liquid chromatography, we believe that the photopigment mediating circadian responses to light is based upon an opsin, and that 11-cis-retinaldehyde is the photopigment chromophore. Preliminary measurements of mouse rod opsin, blue cone, and green-red cone opsin messenger RNA in retinally degenerate mice suggest that none of these opsins is exclusively used to mediate circadian responses to light. Collectively, our data suggest that circadian photoreception can be maintained by a very small number of rod or cone cells without outer segments, or, alternatively, is performed by an unrecognized class of photoreceptive cell within the mammalian retina.