eNeuroApr 5, 2017

Interaction Between the Brain's Internal Clock and Metabolic Control Areas Needed to Organize Body Rhythms

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Mar 25, 2026

Abstract

Microcuts that remove interconnectivity between the (SCN) and (ARC) result in a loss of rhythmicity in locomotor activity, corticosterone levels, and body temperature in Wistar rats.

Loss of SCN-ARC connections led to arrhythmic behavior in constant dark conditions.
SCN clock gene rhythmicity remained intact despite the disconnection from the ARC.
Disconnection caused desynchronization of the ARC, indicating its role in regulating rhythms.
Unilateral SCN lesions combined with microcuts also resulted in similar arrhythmicity.
SCN neuronal activity modulation by metabolism was demonstrated through altered c-Fos expression following glucose administration in disconnected subjects.
These findings suggest the SCN functions within a broader network essential for maintaining homeostasis.

Simplified

The (SCN) is generally considered the master clock, independently driving all circadian rhythms. We recently demonstrated the SCN receives metabolic and cardiovascular feedback adeptly altering its neuronal activity. In the present study, we show that microcuts effectively removing SCN- (ARC) interconnectivity in Wistar rats result in a loss of rhythmicity in locomotor activity, corticosterone levels, and body temperature in constant dark (DD) conditions. Elimination of these reciprocal connections did not affect SCN clock gene rhythmicity but did cause the ARC to desynchronize. Moreover, unilateral SCN lesions with contralateral retrochiasmatic microcuts resulted in identical arrhythmicity, proving that for the expression of physiological rhythms this reciprocal SCN-ARC interaction is essential. The unaltered SCN c-Fos expression following glucose administration in disconnected animals as compared to a significant decrease in controls demonstrates the importance of the ARC as metabolic modulator of SCN neuronal activity. Together, these results indicate that the SCN is more than an autonomous clock, and forms an essential component of a larger network controlling homeostasis. The present novel findings illustrate how an imbalance between SCN and ARC communication through circadian disruption could be involved in the etiology of metabolic disorders.

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Loss of rhythmicity in locomotor activity

All RC-cut animals demonstrated loss of locomotor activity rhythm in DD.

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Corticosterone levels rhythmicity

RC-cut animals exhibited no rhythmic variation in corticosterone levels.

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Melatonin levels rhythmicity

Melatonin levels maintained rhythmicity in both SHAM and RC-cut animals.

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Interaction Between the Brain's Internal Clock and Metabolic Control Areas Needed to Organize Body Rhythms

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