Abraham, Diya Dallmann, Robert Steinlechner, Stephan Albrecht, Urs Eichele, Gregor Oster, Henrik 2006 In mammals, circadian rhythms in behavior and physiology are controlled by a central pacemaker, the SCN, and subordinated clocks throughout the body. On the molecular level, these clocks are based on transcriptional/translational feedback loops involving a set of clock genes that regulate their own transcription. Among the components driving the mammalian circadian clock are the <i>Period 1</i> and <i>2</i> (<i>Per1</i> and <i>Per2</i>) and <i>Cryptochrome 1</i> and <i>2</i> (<i>Cry1</i> and <i>Cry2</i>) genes. In the present study, the authors characterize the behavioral and molecular rhythms of <i>Per2</i>/<i>Cry1</i> double mutant mice under 3 different lighting conditions. In an LD cycle, the activity of these animals is masked by light, while in DD, the mutants lose circadian rhythmicity but exhibit strong ultradian rhythms. In LL of higher intensity, circadian rhythms are restored on the behavioral level with a drastically shortened endogenous period. Furthermore, both in the SCN and in the periphery, clock gene rhythms are restored. Based on these observations and also on the fact that light-mediated induction of <i>Per</i> gene expression is preserved in these mutants, the authors propose a mechanism by which endogenous ultradian rhythms may relay timed light exposure to the SCN, leading to a reinitiation of self-sustained circadian rhythms in LL. application/pdf https://folia.unifr.ch/global/documents/299931 https://folia.unifr.ch/documents/299931/files/albrecht_rcr.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1177/0748730406288040 info:eu-repo/semantics/openAccess License undefined Journal of Biological Rhythms. - 2006, vol. 21, no. 3, p. 169-176 circadian constant light corticosterone cry kidney per SCN ultradian info:eu-repo/classification/udc/61 Restoration of circadian rhythmicity in circadian clock-deficient mice in constant light http://purl.org/coar/resource_type/c_6501