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Neuron. 2017 Mar 22;93(6):1420-1435.e5. doi: 10.1016/j.neuron.2017.02.030. Epub 2017 Mar 9.

Astrocytes Control Circadian Timekeeping in the Suprachiasmatic Nucleus via Glutamatergic Signaling.

Author information

1
Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK. Electronic address: marcob@mrc-lmb.cam.ac.uk.
2
Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
3
Division of Neurobiology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK. Electronic address: mha@mrc-lmb.cam.ac.uk.

Abstract

The suprachiasmatic nucleus (SCN) of the hypothalamus orchestrates daily rhythms of physiology and behavior in mammals. Its circadian (∼24 hr) oscillations of gene expression and electrical activity are generated intrinsically and can persist indefinitely in temporal isolation. This robust and resilient timekeeping is generally regarded as a product of the intrinsic connectivity of its neurons. Here we show that neurons constitute only one "half" of the SCN clock, the one metabolically active during circadian daytime. In contrast, SCN astrocytes are active during circadian nighttime, when they suppress the activity of SCN neurons by regulating extracellular glutamate levels. This glutamatergic gliotransmission is sensed by neurons of the dorsal SCN via specific pre-synaptic NMDA receptor assemblies containing NR2C subunits. Remarkably, somatic genetic re-programming of intracellular clocks in SCN astrocytes was capable of remodeling circadian behavioral rhythms in adult mice. Thus, SCN circuit-level timekeeping arises from interdependent and mutually supportive astrocytic-neuronal signaling.

KEYWORDS:

GABA; NMDAR2C; SCN; astrocytic-neuronal interactions; calcium oscillations; circadian; circadian behavior; circuit synchronization; extracellular glutamate; membrane potential oscillations

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PMID:
28285822
PMCID:
PMC5376383
DOI:
10.1016/j.neuron.2017.02.030
[Indexed for MEDLINE]
Free PMC Article

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