Regional circadian period difference in the suprachiasmatic nucleus of the mammalian circadian center

Jul 23, 2013The European journal of neuroscience

Differences in daily rhythm timing within parts of the brain’s biological clock

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Abstract

The study identified two distinct regions in the suprachiasmatic nucleus (SCN) based on circadian periods: a short-period region (SPR) with periods shorter than 24 hours and a long-period region (LPR) with periods longer than 24 hours.

Disruption of intercellular coupling among SCN neurons revealed regional differences in circadian periods.
The short-period region (SPR) is located in the smaller medial area of the SCN, while the long-period region (LPR) occupies the larger remaining area.
Slices from the medial region of the SCN produced shorter circadian periods compared to slices from the lateral region.
The SPR aligns with the area where the SCN phase wave is generated.
A mathematical model based on these findings successfully simulated the behavior of oscillators in the SCN under synchronized conditions, suggesting the presence of clustered short-period oscillators.

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The suprachiasmatic nucleus (SCN) is the mammalian circadian rhythm center. Individual oscillating neurons have different endogenous circadian periods, but they are usually synchronized by an intercellular coupling mechanism. The differences in the period of each oscillating neuron have been extensively studied; however, the clustering of oscillators with similar periods has not been reported. In the present study, we artificially disrupted the intercellular coupling among oscillating neurons in the SCN and observed regional differences in the periods of the oscillating small-latticed regions of the SCN using a transgenic rat carrying a luciferase reporter gene driven by regulatory elements from a per2 clock gene (Per2::dluc rat). The analysis divided the SCN into two regions--aregion with periods shorter than 24 h (short-period region, SPR) and another with periods longer than 24 h (long-period region, LPR). The SPR was located in the smaller medial region of the dorsal SCN, whereas the LPR occupied the remaining larger region. We also found that slices containing the medial region of the SCN generated shorter circadian periods than slices that contained the lateral region of the SCN. Interestingly, the SPR corresponded well with the region where the SCN phase wave is generated. We numerically simulated the relationship between the SPR and a large LPR. A mathematical model of the SCN based on our findings faithfully reproduced the kinetics of the oscillators in the SCN in synchronized conditions, assuming the existence of clustered short-period oscillators.

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Regional circadian period difference in the suprachiasmatic nucleus of the mammalian circadian center

Abstract

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