Aging does not compromise in vitro oscillation of the suprachiasmatic nuclei but makes it more vulnerable to constant light

Oct 30, 2016Chronobiology international

Aging does not reduce the internal clock rhythm in brain’s time-keeping center but makes it more sensitive to constant light

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Abstract

Under constant light conditions, 47% of aged mice exhibited completely arrhythmic SCN explants compared to 27% of adult mice.

Aging may impair the circadian regulation of behavior, particularly under unnatural lighting conditions.
Increased age correlates with a marginal decline in rhythmicity in the middle region of the suprachiasmatic nuclei (SCN) under constant light.
The ability of the SCN to produce bioluminescence rhythms in vitro remains relatively unaffected by aging in standard light/dark cycles or constant darkness.
Aging significantly impacts locomotor activity rhythms driven by the SCN despite the resilience of the core molecular clock mechanism.
Findings suggest that age-related changes in circadian rhythms may involve pathways beyond the core clock mechanism.

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Circadian regulation of behavior worsens with age, however, the mechanism behind this phenomenon is still poorly understood. Specifically, it is not clear to what extend the ability of the circadian clock in the suprachiasmatic nuclei (SCN) to generate the rhythm is affected by aging. This study aimed to ascertain the effect of aging on the functioning of the SCN of mPer2mice under unnatural lighting conditions, such as constant light (LL). Under LL, which worsened the age-induced effect on behavioral rhythms, a marginal age-dependent effect on in vitro rhythmicity in explants containing the middle, but not the rostral/caudal, regions of the SCN was apparent; the proportion of mice in which middle-region SCN explants were completely arrhythmic or had an extremely long period (>30 h) was 47% in aged mice and 27% in adults. The results suggest that in some of the aged animals, LL may weaken the coupling among oscillators in specific sub-regions of the SCN, leaving other sub-regions better synchronized. In the standard light/dark cycle and in constant darkness, the SCN ability to produce bioluminescence rhythms in vitro was not compromised in aged mice although aging significantly affected their SCN-driven locomotor activity rhythms. Therefore, our results demonstrate that although age worsened the SCN output rhythm, the SCN molecular core clock mechanism itself was relatively resilient to aging in these same animals. The results suggest the involvement of pathways downstream of the core clock mechanism which are responsible for this phenomenon. Luciferase

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Aging does not compromise in vitro oscillation of the suprachiasmatic nuclei but makes it more vulnerable to constant light

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