Faculty Opinions recommendation of Dual regulation of clock gene Per2 expression in discrete brain areas by the circadian pacemaker and methamphetamine-induced oscillator in rats.

Circadian rhythms in clock gene expressions in the suprachiasmatic nucleus (SCN) of CS mice and C57BL/6J mice were measured under a daily restricted feeding (RF) schedule in continuous darkness (DD), and entrainment of the SCN circadian pacemaker to RF was examined. After 2–3 wk under a light-dark cycle with free access to food, animals were released into DD and fed for 3 h at a fixed time of day for 3–4 wk. Subsequently, they returned to having free access to food for 2–3 wk. In CS mice, wheel-running rhythms entrained to RF with a stable phase relationship between the activity onset and feeding time, and the rhythms started to free run from the feeding time after the termination of RF. mPer1, mPer2, and mBMAL1 mRNA rhythms in the SCN showed a fixed phase relationship with feeding time, indicating that the circadian pacemaker in the SCN entrained to RF. On the other hand, in C57BL/6J mice, wheel-running rhythms free ran under RF, and clock gene expression rhythms in the SCN showed a stable phase relation not to feeding time but to the behavioral rhythms, indicating that the circadian pacemaker in the SCN did not entrain. These results indicate that the SCN circadian pacemaker of CS mice is entrainable to RF under DD and suggest that CS mice have a circadian clock system that can be reset by a signal associated with feeding time.

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The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids

Endocrine Reviews ◽

10.1210/er.2015-1080 ◽

2016 ◽

Vol 38 (1) ◽

pp. 3-45 ◽

Cited By ~ 107

Author(s):

Henrik Oster ◽

Etienne Challet ◽

Volker Ott ◽

Emanuela Arvat ◽

E. Ronald de Kloet ◽

...

Keyword(s):

Stress Responses ◽

Adrenal Glands ◽

Circadian Pacemaker ◽

Brain Areas ◽

Peripheral Tissues ◽

The Past ◽

Molecular Machinery ◽

Health And Disease ◽

Peripheral Clocks

Abstract Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has long been recognized that this 24-hour rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus. In the past decade, secondary circadian clocks based on the same molecular machinery as the central master pacemaker were found in other brain areas as well as in most peripheral tissues, including the adrenal glands. Evidence is rapidly accumulating to indicate that misalignment between central and peripheral clocks has a host of adverse effects. The robust rhythm in circulating glucocorticoid levels has been recognized as a major internal synchronizer of the circadian system. The present review examines the scientific foundation of these novel advances and their implications for health and disease prevention and treatment.

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The period clock gene is expressed in central nervous system neurons which also produce a neuropeptide that reveals the projections of circadian pacemaker cells within the brain of Drosophila melanogaster.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.92.2.612 ◽

1995 ◽

Vol 92 (2) ◽

pp. 612-616 ◽

Cited By ~ 260

Author(s):

C. Helfrich-Forster

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Drosophila Melanogaster ◽

Clock Gene ◽

Circadian Pacemaker ◽

Pacemaker Cells ◽

The Brain

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Circadian neurons in the paraventricular nucleus entrain and sustain daily rhythms in glucocorticoids

Nature Communications ◽

10.1038/s41467-021-25959-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jeff R. Jones ◽

Sneha Chaturvedi ◽

Daniel Granados-Fuentes ◽

Erik D. Herzog

Keyword(s):

Paraventricular Nucleus ◽

Clock Gene ◽

Hormone Release ◽

Circadian Pacemaker ◽

Daily Rhythms ◽

Calcium Activity ◽

Clock Gene Expression ◽

Corticosterone Release ◽

Critical Circuit

AbstractSignals from the central circadian pacemaker, the suprachiasmatic nucleus (SCN), must be decoded to generate daily rhythms in hormone release. Here, we hypothesized that the SCN entrains rhythms in the paraventricular nucleus (PVN) to time the daily release of corticosterone. In vivo recording revealed a critical circuit from SCN vasoactive intestinal peptide (SCNVIP)-producing neurons to PVN corticotropin-releasing hormone (PVNCRH)-producing neurons. PVNCRH neurons peak in clock gene expression around midday and in calcium activity about three hours later. Loss of the clock gene Bmal1 in CRH neurons results in arrhythmic PVNCRH calcium activity and dramatically reduces the amplitude and precision of daily corticosterone release. SCNVIP activation reduces (and inactivation increases) corticosterone release and PVNCRH calcium activity, and daily SCNVIP activation entrains PVN clock gene rhythms by inhibiting PVNCRH neurons. We conclude that daily corticosterone release depends on coordinated clock gene and neuronal activity rhythms in both SCNVIP and PVNCRH neurons.

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