In synch but not in step: Circadian clock circuits regulating plasticity in daily rhythms

Evans, Jennifer; Gorman, Michael R.

doi:10.1016/j.neuroscience.2016.01.072

Cited by 40 publications

(49 citation statements)

References 282 publications

(440 reference statements)

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“…Plasticity of the neuronal network within the SCN is necessary for day-length encoding and proper re-entrainment, but the underlying detailed mechanisms are still largely elusive [27]. We analyzed PER2::LUC gene expression rhythms of single SCN neurons of mice exposed to different photoperiods to investigate the dynamic behavior of clock neurons at different synchronized states.…”

Section: Discussionmentioning

confidence: 99%

Evidence for Weakened Intercellular Coupling in the Mammalian Circadian Clock under Long Photoperiod

et al. 2016

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For animals living in temperate latitudes, seasonal changes in day length are an important cue for adaptations of their physiology and behavior to the altered environmental conditions. The suprachiasmatic nucleus (SCN) is known as the central circadian clock in mammals, but may also play an important role in adaptations to different photoperiods. The SCN receives direct light input from the retina and is able to encode day-length by approximating the waveform of the electrical activity rhythm to the duration of daylight. Changing the overall waveform requires a reorganization of the neuronal network within the SCN with a change in the degree of synchrony between the neurons; however, the underlying mechanisms are yet unknown. In the present study we used PER2::LUC bioluminescence imaging in cultured SCN slices to characterize network dynamics on the single-cell level and we aimed to provide evidence for a role of modulations in coupling strength in the photoperiodic-induced phase dispersal. Exposure to long photoperiod (LP) induced a larger distribution of peak times of the single-cell PER2::LUC rhythms in the anterior SCN, compared to short photoperiod. Interestingly, the cycle-to-cycle variability in single-cell period of PER2::LUC rhythms is also higher in the anterior SCN in LP, and is positively correlated with peak time dispersal. Applying a new, impartial community detection method on the time series data of the PER2::LUC rhythm revealed two clusters of cells with a specific spatial distribution, which we define as dorsolateral and ventromedial SCN. Post hoc analysis of rhythm characteristics of these clusters showed larger cycle-to-cycle single-cell period variability in the dorsolateral compared to the ventromedial cluster in the anterior SCN. We conclude that a change in coupling strength within the SCN network is a plausible explanation to the observed changes in single-cell period variability, which can contribute to the photoperiod-induced phase distribution.

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Section: Discussionmentioning

confidence: 99%

Evidence for Weakened Intercellular Coupling in the Mammalian Circadian Clock under Long Photoperiod

et al. 2016

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“…There are a number of excellent reviews of SCN neuroanatomy that discuss the issues related to SCN subdivisions, so we provide only a brief background and discussion here (Moore et al, 2002; Hastings and Herzog, 2004; Lee et al, 2003; Antle et al, 2009; Morin, 2007; Antle and Silver, 2005; Yan et al, 2007; Yan, 2009; Evans, 2016; Evans and Gorman, 2016). Historically, each side of the bilaterally paired SCN has been divided into two regions (although a third division has been described as well) (Morin, 2007).…”

Section: Suprachiasmatic Nucleus (Scn): Functional Anatomical Anmentioning

confidence: 99%

The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus

Albers

Walton

Gamble

et al. 2017

Frontiers in Neuroendocrinology

133

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Virtually every neuron within the suprachiasmatic nucleus (SCN) communicates via GABAergic signaling. The extracellular levels of GABA within the SCN are determined by a complex interaction of synthesis and transport, as well as synaptic and non-synaptic release. The response to GABA is mediated by GABAA receptors that respond to both phasic and tonic GABA release and that can produce excitatory as well as inhibitory cellular responses. GABA also influences circadian control through the exclusively inhibitory effects of GABAB receptors. Both GABA and neuropeptide signaling occur within the SCN, although the functional consequences of the interactions of these signals are not well understood. This review considers the role of GABA in the circadian pacemaker, in the mechanisms responsible for the generation of circadian rhythms, in the ability of non-photic stimuli to reset the phase of the pacemaker, and in the ability of the day-night cycle to entrain the pacemaker.

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“…SCN neurons are highly interconnected and can influence each other's electrical and molecular rhythmicity (Colwell, 2011;Mohawk and Takahashi, 2011;Van Den Pol and Dudek, 1993). Input derived from rhythmic external cues as well as rhythmic internal signals (feedback) can modulate the molecular and electrophysiological rhythms of SCN neurons, altering the phase, period and waveform of the generated rhythm (see reviews by Evans and Gorman, 2016;Yannielli and Harrington, 2004 for details).…”

Section: The Regulation Of Daily Rhythms In Mammalsmentioning

confidence: 99%

The flexible clock: predictive and reactive homeostasis, energy balance and the circadian regulation of sleep–wake timing

Riede

Vinne

Hut

2017

Journal of Experimental Biology

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The Darwinian fitness of mammals living in a rhythmic environment depends on endogenous daily (circadian) rhythms in behavior and physiology. Here, we discuss the mechanisms underlying the circadian regulation of physiology and behavior in mammals. We also review recent efforts to understand circadian flexibility, such as how the phase of activity and rest is altered depending on the encountered environment. We explain why shifting activity to the day is an adaptive strategy to cope with energetic challenges and show how this can reduce thermoregulatory costs. A framework is provided to make predictions about the optimal timing of activity and rest of non-model species for a wide range of habitats. This Review illustrates how the timing of daily rhythms is reciprocally linked to energy homeostasis, and it highlights the importance of this link in understanding daily rhythms in physiology and behavior.

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In synch but not in step: Circadian clock circuits regulating plasticity in daily rhythms

Cited by 40 publications

References 282 publications

Evidence for Weakened Intercellular Coupling in the Mammalian Circadian Clock under Long Photoperiod

Evidence for Weakened Intercellular Coupling in the Mammalian Circadian Clock under Long Photoperiod

The dynamics of GABA signaling: Revelations from the circadian pacemaker in the suprachiasmatic nucleus

The flexible clock: predictive and reactive homeostasis, energy balance and the circadian regulation of sleep–wake timing

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