# RHYTHMS, REPRODUCTION, AND PHOTORECEPTION IN MAMMALS

> **NIH NIH R01** · UNIVERSITY OF VIRGINIA · 1994 · $126,686

## Abstract

Circadian rhythmicity is a critically important component of the temporal
organization of most living things. Work with mammalian models has
established that the circadian pacemaking system, located in the
suprachiasmatic nucleus, influences the timing of many behavioral,
physiological and endocrinological processes. In humans, disruption of
the circadian system produced by travel across time zones causes jet lag,
fatigue and general decline in alertness and performance. The circadian
system is affected adversely in old people, and such effects may well
underlie the almost universal difficulties with insomnia experienced by
the aged. Abnormalities in circadian physiology which may result from
environmental insult or from genetic anomalies are thought to be
partially responsible for much more serious pathologies such as some
forms of severe depression.

Until the discovery of the tau mutant hamster, there have been no genetic
models available with which to investigate the many roles of the
mammalian circadian system. The tau gene is a single, co-dominant,
autosomal gene: wild-type hamsters have free-running circadian periods
of 24 hours, hamsters heterozygous for the mutant allele have periods of
22 hours, and homozygous mutants have periods of 20 hours. We propose to
use the mutation to study the roles played by the circadian system in the
regulation or modulation of other non-circadian aspects of mammalian
temporal organization. We will determine how the changes in the circadian
system that is produced by the tau mutation affect three endocrine-
mediated rhythms of very different frequencies: LH pulses produced at
roughly 20 minute intervals by the pituitary; estrous cyclicity which in
wild-type hamsters has a period of four days; and the annual reproductive
cycle which is regulated by the seasonal changes in daylength
(photoperiod). We have preliminary evidence which indicates that each of
these three processes is affected by the mutation. Our experiments are
directed toward understanding of the mechanisms that are responsible for
these effects.  This knowledge will deepen our understanding of mammalian
temporal organization by defining the place of the circadian pacemaker
in the temporal hierarchy and the ways in which it interacts with other
biological oscillations.

## Key facts

- **NIH application ID:** 2196970
- **Project number:** 5R01HD013162-14
- **Recipient organization:** UNIVERSITY OF VIRGINIA
- **SAM.gov UEI:** JJG6HU8PA4S5
- **Principal Investigator:** MICHAEL MENAKER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1994
- **Award amount:** $126,686
- **Award type:** 5
- **Project period:** 1987-07-01 → 1997-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/2196970

## Citation

> US National Institutes of Health, RePORTER application 2196970, RHYTHMS, REPRODUCTION, AND PHOTORECEPTION IN MAMMALS (5R01HD013162-14). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/2196970. Licensed CC0.

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