Hierarchical organization of the circadian timing system

Steensel, M.J. van (2006)

Doctoral Thesis

In order to cope with and to predict 24-hour rhythms in the environment, most, if not all, organisms have a circadian timing system. The most important mammalian circadian pacemaker is located in the suprachiasmatic nucleus at the base of the hypothalamus in the brain. Over the years, it has become clear that the circadian system is complex and that additional oscillators exist, both within and outside the central nervous system. The aim of this thesis was to obtain insight in the hierarchical organization of the circadian timing system and to determine whether certain attributes arise at the tissue level. The data reveal that interactions between the SCN and the periphery, as well as interactions between subregions within the SCN, contribute significantly to the functioning of the circadian system. Another important finding is that the multiple components of the circadian system can, under certain circumstances, dissociate. The hierarchical organization of the circadian timing system, the interactions between and within organizational levels, and importantly, the ability of several components to dissociate, may provide the circadian system the required plasticity to adjust to biologically relevant changes in the environment.

• Circadian rhythms
• Suprachiasmatic nucleus
• Clock genes
• Oscillator
• Electrophysiology
• Entrainment
• Sleep
• GABA
• Biological clock
• Time

• All authors: Steensel, M.J. van
• Supervisor: Tanke, H.J.; Meijer, J.H.
• Co-supervisor: Meijer J.H.
• Qualification: Doctor (dr.)
• Awarding Institution: Faculty of Medicine, Leiden University Medical Center (LUMC), Leiden University
• Date: 2006-06-21
• ISBN (print): 9789090206103
• Court: LEI Universiteit Leiden