Separating morning and evening in the circadian clock of mammals

Jun 24, 2005

Work by researchers at the universities of Aberdeen and Nottingham suggest an anatomical basis for the adaptation of the mammalian circadian clock to changing day-length.
Endogenous circadian clocks ensure that temporal patterns of physiology and behavior predict environmental changes determined by the Earth’s rotation and orbit of the Sun. Such clocks are synchronized by the daily light-dark cycle.

A key question for circadian biologists concerns the way in which seasonal changes in day-length alter the behavior of circadian clocks over the course of the year. One idea for which evidence has accumulated is that circadian clocks contain coupled “morning” and “evening” oscillators that are separately synchronized to dawn and dusk.

In the new work, published in this week’s issue of Current Biology, Dr David Hazlerigg and colleagues considered the possibility that distinct populations of neurons within the principal mammalian circadian clock (the suprachiasmatic nuclei of the hypothalamus, SCN) might constitute these different oscillators. By measuring gene-expression rhythms in the SCN of hamsters held on different day-lengths, they were able to show that cells in the caudal region of the SCN synchronize their gene-expression rhythms to dawn and, when the day-length is increased, exhibit earlier peak expression relative to midday.

The researchers also report a lesser, but opposite, response in cells in another group of neurons, the rostral SCN. Hence, synchronous gene expression across the SCN may be a hallmark of short-day acclimation, whereas regional de-synchrony increases on long days.

Further studies are needed to discern whether this phenomenon translates into distinctive day-length-induced changes in rhythmic output from different regions of the SCN. Abnormalities in the adaptation of the SCN to changing day-length may underlie the development of seasonal affective disorder (SAD) in humans.

Source: University of Aberdeen

Explore further: Team discovers first evidence of milk consumption in ancient dental plaque

add to favorites email to friend print save as pdf

Related Stories

NASA issues 'remastered' view of Jupiter's moon Europa

26 minutes ago

(Phys.org) —Scientists have produced a new version of what is perhaps NASA's best view of Jupiter's ice-covered moon, Europa. The mosaic of color images was obtained in the late 1990s by NASA's Galileo ...

Dish restores Turner channels to lineup

43 minutes ago

Turner Broadcasting channels such as Cartoon Network and CNN are back on the Dish network after being dropped from the satellite TV provider's lineup during contract talks.

LiquidPiston unveils quiet X Mini engine prototype

5 hours ago

LiquidPiston has a new X Mini engine which is a small 70 cubic centimeter gasoline powered "prototype. This is a quiet, four-stroke engine with near-zero vibration. The company said it can bring improvements ...

Recommended for you

Golden Ratio offers unity of science

5 hours ago

It is said to represent a "cosmic constant" found in the curvature of elephant tusks, the shape of a kudu's horn, the destructive beauty of Hurricane Katrina, and in the astronomical grandeur of how planets, ...

Consumer sentiment brightens holiday spending

8 hours ago

Consumer confidence posted its fourth consecutive monthly gain in November, rising to its highest level since July 2007, according to the Thomson Reuters/University of Michigan Surveys of Consumers.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.