Age‐Related Effects on the Biological Clock and its Behavioral Output in a Primate

May 12, 2006Chronobiology international

How Aging Affects the Body’s Internal Clock and Daily Behavior in Primates

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Abstract

Aged mouse lemurs exhibited a significant increase in daytime activity and an advanced activity onset compared to adults.

Older mouse lemurs showed a shortening of the free-running period when kept in constant dim red light.
In aged mouse lemurs, peaks of arginine-vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) immunoreactivity were significantly shifted without a change in amplitude.
AVP immunoreactivity was most intense at the beginning of the night in aged animals, while VIP immunoreactivity peaked at the start of the daytime.
These findings suggest that age-related changes in the circadian system may impact the expression of biological rhythms.

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In humans, activity rhythms become fragmented and attenuated in the elderly. This suggests an alteration of the circadian system per se that could in turn affect the expression of biological rhythms. In primates, very few studies have analyzed the effect of aging on the circadian system. The mouse lemur provides a unique model of aging in non-human primates. To assess the effect of aging on the circadian system of this primate, we recorded the circadian and daily rhythms of locomotor activity of mouse lemurs of various ages. We also examined age-related changes in the daily rhythm of immunoreactivities for vasoactive intestinal polypeptide (VIP) and arginine-vasopressin (AVP) in suprachiasmatic nucleus neurons (SCN), two major peptides of the biological clock. Compared to adult animals, aged mouse lemurs showed a significant increase in daytime activity and an advanced activity onset. Moreover, when maintained in constant dim red light, aged animals exhibited a shortening of the free-running period compared to adult animals. In adults, AVP immunoreactivity (ir) peaked during the second part of the day, and VIP ir peaked during the night. In aged mouse lemurs, the peaks of AVP ir and VIP ir were significantly shifted with no change in amplitude. AVP ir was most intense at the beginning of the night; whereas, VIP ir peaked at the beginning of the daytime. A weakened oscillator could account for the rhythmic disorders often observed in the elderly. Changes in the daily rhythms of AVP ir and VIP ir may affect the ability of the SCN to transmit rhythmic information to other neural target sites, and thereby modify the expression of some biological rhythms.

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Age‐Related Effects on the Biological Clock and its Behavioral Output in a Primate

Abstract

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