科研之友
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摘要
The suprachiasmatic nucleus (SCN) is the master circadian pacemaker in the mammalian brain, responsible for coordinating circadian (ca 24 h) rhythms throughout the body. When individual SCN neurons are dispersed in low density culture, they generate independent circadian oscillations in neuronal firing rate. This observation has led to the widely accepted conclusion that single SCN neurons are autonomous circadian oscillators. More recent studies using bioluminescence imaging to monitor rhythms of clock gene expression have indicated that fibroblasts, too, are autonomous circadian oscillators. But does this mean that the fibroblast should "replace the SCN as the in vitro model of choice"? On the contrary, the SCN is much more than a population of independent cellular oscillators. SCN function depends on important network interactions that allow for cell synchrony, enhanced pacemaker precision, reinforcement of rhythm amplitude, and robustness against genetic perturbations. The distribution of phases of cells within the SCN network also permits variously phased rhythmic output signals, as well as the encoding of seasonal changes in photoperiod and other features of environmental lighting history. Thus, unlike fibroblasts, SCN neurons are designed to be "team players," and SCN network interactions are integral to the normal function of the SCN as a circadian pacemaker.
- 出版日期2009-10
