From clock to functional pacemaker

• Published in: The European journal of neuroscience Vol. 51; no. 1; pp. 482 - 493
• Main Authors: Michel, Stephan, Meijer, Johanna H.
• Format: Journal Article
• Language: English
• Published: France Wiley Subscription Services, Inc 01.01.2020; John Wiley and Sons Inc
• Subjects: Aging; Cell interactions; Circadian rhythms; Circadian Rhythms ‐ Special Issue; in vivo electrophysiology; networks; Neurons; Oscillators; Pacemakers; photoperiod; Physical activity; Rhythm; SCN; Special Issue Review; Suprachiasmatic nucleus; Synchronization; in vivo electrophysiology; synchronization; networks; photoperiod; SCN
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/ejn.14388

In mammals, the central pacemaker that coordinates 24‐hr rhythms is located in the suprachiasmatic nucleus (SCN). Individual neurons of the SCN have a molecular basis for rhythm generation and hence, they function as cell autonomous oscillators. Communication and synchronization among these neurons are crucial for obtaining a coherent rhythm at the population level, that can serve as a pace making signal for brain and body. Hence, the ability of single SCN neurons to produce circadian rhythms is equally important as the ability of these neurons to synchronize one another, to obtain a bona fide pacemaker at the SCN tissue level. In this chapter we will discuss the mechanisms underlying synchronization, and plasticity herein, which allows adaptation to changes in day length. Furthermore, we will discuss deterioration in synchronization among SCN neurons in aging, and gain in synchronization by voluntary physical activity or exercise. All our bodily functions show 24‐hr patters, in order to increase fitness in an everchanging environment. It is phenomenal that these global rhythms rely on a handful of tiny oscillating neurons in the suprachiasmatic nuclei (SCN) that synchronize to the environmental cycle via a primitive retinal pathway. The neurons of the SCN have the extraordinary capacity to function as a pacemaker, and by their responsiveness to internal cues, they form an integrated circadian system subserving health.