# EFFECTS OF AGE ON MAMMALIAN CIRCADIAN CLOCK

> **NIH NIH R01** · NORTHWESTERN UNIVERSITY · 1991 · $143,062

## Abstract

Although a variety of stimuli have been identified which can alter the
circadian clock system of young animals, little is known about how aging
alters the response of the clock to external and internal environmental
stimuli.  Preliminary data in the golden hamster demonstrate that the
response of the circadian clock system to the primary external
environmental synchronizing agent, light, is dramatically altered in old
age (i.e. > 18 months of age).  In addition, with advanced age the
circadian clock in this species appears to become unresponsive to feedback
signals about the activity-rest state.  The overall objectives of the
proposed studies are, 1) to determine in detail how the response of the
circadian clock system to light or changes in the activity-rest state is
altered in old age, and 2) to determine the physiological basis for age-
related changes in the response of the circadian clock to environmental
stimuli.

To examine the effects of aging on the response of the circadian system to
various stimuli, the circadian rhythm of locomotor activity in golden
hamsters will be used as a marker rhythm for the state of the circadian
clock located in the suprachiasmatic nucleus (SCN) that underlies most
behavioral and physiological rhythms in this species.  With respect to age-
related changes in the response of the clock to light, a series of
experiments will be carried out to determine 1) the extent to which aging
alters both the phase-shifting and entraining effects of light, and 2)
whether age-related alterations in the response to light are due to changes
in the reception of photic information or to changes at the level of the
SCN.  Whether age-related changes in the response of the clock to light are
associated with an alteration in light-induced protein synthesis within the
SCN will also be determined.  With respect to age-related changes in the
response of the clock to signals about the activity-rest state, a series of
experiments will be carried out to determine 1) if the circadian clock of
old animals is completely insensitive to the phase shifting effects of
various stimuli that induce acute changes in the activity state, as well as
phase shifts in the circadian clock of young animals, and 2) the age at
which the circadian clock becomes totally or partially insensitive to the
phase-shifting effects of feedback signals about the activity-rest state of
the animal.  In view of recent findings indicating that norepinephrine may
be involved in mediating the effects of stimulated activity on the
circadian clock, a series of experiments will be carried out to determine
if age-related changes in central noradrenergic activity underlie the loss
of responsiveness to such stimuli with advanced age, and whether the
response of the circadian clock to such stimuli can be restored by
increasing central adrenergic activity in old animals.

In addition to providing new insight into how the response of the circadian
clock system to external and internal ...

## Key facts

- **NIH application ID:** 3121127
- **Project number:** 1R01AG009297-01A1
- **Recipient organization:** NORTHWESTERN UNIVERSITY
- **SAM.gov UEI:** EXZVPWZBLUE8
- **Principal Investigator:** FRED W TUREK
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1991
- **Award amount:** $143,062
- **Award type:** 1
- **Project period:** 1991-05-01 → 1996-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3121127

## Citation

> US National Institutes of Health, RePORTER application 3121127, EFFECTS OF AGE ON MAMMALIAN CIRCADIAN CLOCK (1R01AG009297-01A1). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3121127. Licensed CC0.

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