| First Author | Nakamura TJ | Year | 2011 |
| Journal | PLoS One | Volume | 6 |
| Issue | 12 | Pages | e28726 |
| PubMed ID | 22216107 | Mgi Jnum | J:182336 |
| Mgi Id | MGI:5315233 | Doi | 10.1371/journal.pone.0028726 |
| Citation | Nakamura TJ, et al. (2011) Reduced light response of neuronal firing activity in the suprachiasmatic nucleus and optic nerve of Cryptochrome-deficient mice. PLoS One 6(12):e28726 |
| abstractText | To examine roles of the Cryptochromes (Cry1 and Cry2) in mammalian circadian photoreception, we recorded single-unit neuronal firing activity in the suprachiasmatic nucleus (SCN), a primary circadian oscillator, and optic nerve fibers in vivo after retinal illumination in anesthetized Cry1 and Cry2 double-knockout (Cry-deficient) mice. In wild-type mice, most SCN neurons increased their firing frequency in response to retinal illumination at night, whereas only 17% of SCN neurons responded during the daytime. However, 40% of SCN neurons responded to light during the daytime, and 31% of SCN neurons responded at night in Cry-deficient mice. The magnitude of the photic response in SCN neurons at night was significantly lower (1.3-fold of spontaneous firing) in Cry-deficient mice than in wild-type mice (4.0-fold of spontaneous firing). In the optic nerve near the SCN, no difference in the proportion of light-responsive fibers was observed between daytime and nighttime in both genotypes. However, the response magnitude in the light-activated fibers (ON fibers) was high during the nighttime and low during the daytime in wild-type mice, whereas this day-night difference was not observed in Cry-deficient mice. In addition, we observed day-night differences in the spontaneous firing rates in the SCN in both genotypes and in the fibers of wild-type, but not Cry-deficient mice. We conclude that the low photo response in the SCN of Cry-deficient mice is caused by a circadian gating defect in the retina, suggesting that Cryptochromes are required for appropriate temporal photoreception in mammals. |
