Interplay of neuronal networks modulates mammalian circadian rhythms

Ramkisoensing, A. (2016)

Doctoral Thesis

 

The suprachiasmatic nucleus (SCN) functions as a circadian clock that drives 24-hour rhythms in physiology and behavior. The SCN neurons function as cell-autonomous oscillators, and the production of a coherent SCN rhythm is dependent upon synchronization among single cells. We investigated how changes in phase-synchronization between individual cells effect the ability of the SCN to phase-shift its rhythm. Empirical and modelling studies revealed larger phase-shifts in synchronized SCN than in desynchronized SCN. The major external stimulus affecting the SCN is light. We explored the ability of melanopsin and rod- and cone photoreceptors to mediate the effects of light on SCN discharge, and found that melanopsin and cones are able to mediate light responses of the SCN. Studies performed in nocturnal species have indicated that the SCN’s rhythmicity is also influenced by the animal’s own behavioral activity. We assessed the effect behavioral activity on the amplitude of the circadian rhythm in SCN electrical discharge rate in the day-active Arvicanthis ansorgei. The results showed acute enhancements of SCN discharge during episodes of behavioral activity. The studies described in this thesis indicate that the SCN is part of a brain network that includes the retina and areas involved in behavioral activity and sleep.

 

• Suprachiasmatic nuclei
• Electrophysiology
• Photoperiod
• Network
• Photoreceptors
• Diurnal
• Behaviour
• Clock

• All authors: Ramkisoensing, A.
• Supervisor: Meijer, J.H.
• Co-supervisor: Rohling, J.H.T.
• Committee: Rensen, P.C.N.; Jager, M.J.; Roenneberg, T.; Vyazovskiy, V.V.; Challet, E.
• Qualification: Doctor (dr.)
• Awarding Institution: Medicine, Leiden University
• Date: 2016-06-07
• ISBN (print): 9789462332942