The experimental research in this thesis aims to gain more understanding of how the SCN network is organized and what is needed for network changes. More specifically, this work focused on the... Show moreThe experimental research in this thesis aims to gain more understanding of how the SCN network is organized and what is needed for network changes. More specifically, this work focused on the potential role of GABA and the GABAeric E/I balance in SCN network plasticity. Communication and synchronization in the SCN are important for the generation of a strong and coherent output signal. Under certain conditions, like long photoperiod, the phases of the individual SCN cells are more dispersed over the 24 hour cycle as evidenced by measurements of electrical activity and clock gene expression. Aging is also known to affect the network organization of the SCN with deterioration in synchronization among the individual SCN neurons. In this thesis, I present work that contributes to research questions regarding the effect of light exposure and/or aging on several characteristics of SCN network plasticity. Show less
Many organisms have developed an internal clock to cope with the daily and seasonal cycles in the environment. In mammals, suprachiasmatic nuclei (SCN) of the hypothalamus control circadian rhythms... Show moreMany organisms have developed an internal clock to cope with the daily and seasonal cycles in the environment. In mammals, suprachiasmatic nuclei (SCN) of the hypothalamus control circadian rhythms in behavior and physiology. Evidence links the proper function of circadian clock to mental and physical health. Aging disturbs the accurate function of the SCN and impairs many rhythms such as sleep-wake cycle. Hence improvement of clock function can aid healthy aging. In chapters 3 and 4 I show the ensemble output of the SCN neuronal network is more robust than individual cells__ output suggesting a compensatory role of the network in aging. Seasonal changes affect the physiology and reproduction success of many organisms. The SCN encodes for day-length by adjusting the pattern of its electrical activity rhythm.. In chapters 5 and 6 I reveal that plasticity in interneuronal and cell-intrinsic functions in the SCN helps the organism to adjust to yearly natural changes in photoperiod. These results imply that extensive artificial light in modern society may alter neurotransmitters action in the SCN. A better understanding of SCN network function and cellular properties facilitate alleviation of modern life-related diseases caused by circadian disturbances and aging. Show less
