Preservation of light signaling to the suprachiasmatic nucleus in vitamin A-deficient mice

To investigate the role of retinal-based pigments (opsins) in circadian pho toreception in mice, animals mutated in plasma retinol binding protein were placed on a vitamin A-free diet and tested for photic induction of gene ex pression in the suprachiasmatic nucleus. After 10 months on the vitamin A-f ree diet, the majority of mice contained no detectable retinal in their eye s. These mice demonstrated fully intact photic signaling to the suprachiasm atic nucleus as measured by acute mPer mRNA induction in the suprachiasmati c nucleus in response to bright or dim light. The data suggest that a non-o psin pigment is the primary circadian photoreceptor in the mouse.