Featured Research

from universities, journals, and other organizations

Sleepless Aged Rats Show Biological Clock Problems

Date:
August 14, 2001
Source:
Washington University In St. Louis
Summary:
One of the problems of the aged is getting a good night’s sleep. Often, the elderly sleep fitfully through the night only to be overcome by drowsiness during the day and nodding off then. A general feeling of tiredness and irritability goes hand-in-hand with this condition. Now a biologist at Washington University in St. Louis and colleagues from France and the University of Virginia have found this problem may be traced to a faulty biological clock — at least in aged rats.

One of the problems of the aged is getting a good night’s sleep. Often, the elderly sleep fitfully through the night only to be overcome by drowsiness during the day and nodding off then. A general feeling of tiredness and irritability goes hand-in-hand with this condition. Now a biologist at Washington University in St. Louis and colleagues from France and the University of Virginia have found this problem may be traced to a faulty biological clock — at least in aged rats. Erik Herzog, Ph.D., assistant professor of biology at Washington University, examined cells involved in the generation of circadian rhythms — the 24-hour cycles in things like alertness and hormone levels. In collaboration with Fabienne Aujard, D.V.M., Ph.D., of France’s Centre National de la Recherche Scientifique, and Gene Block, Ph.D., professor of biology at the University of Virginia, Herzog found that the electrical activity of the clock cells in aged rats was not regular compared with that of young and middle-aged rats.

"In the case of the aged rats, many of them showed fragmented behavioral rhythms," Herzog explained. "They were still rhythmic, but showed bouts of activity when the rats normally would have rested and inactivity when the young animals were active. "So, the rats, like elderly humans, took naps when they would have normally been active. Remarkably, the cells in their biological clock reflected this behavior."

The research is supported by the National Institutes of Health and will be published in the forthcoming issue of Neuroscience. Herzog cannot surmise exactly what role aging is playing in this irregularity, but he doesn’t think it’s a result of the circadian rhythm network breaking down.

"The deterioration of rhythmicity would appear to be a single cell property," he said. "The individual pacemaker cells appear to be losing their ability to mark time. We could argue that this is evidence of aging acting at the level of single cells."

The hub of circadian rhythm in rats and humans and other mammals is found in the suprachiasmatic nucleus (SCN), a part of the hypothalamus that can be found on the bottom of the brain just above the roof of your mouth where your optic nerves cross. There are roughly 10,000 cells in this nucleus. The timekeeping mechanism in these cells depends on daily cycles in gene activity. The first of these genes identified in mammals was called CLOCK, for "circadian locomotor output cycles kaput."

The first thing that Herzog and his collaborators have established in studying this region is that SCN neurons can act as autonomous pacemakers, keeping time without input from other cells. While the SCN is required for circadian rhythmicity, there are other circadian oscillators in the body and in different parts of the brain. However, without the SCN, other circadian rhythms disappear. Herzog and his colleagues study rat SCN cells in vitro — outside the body — and hope to gain knowledge of how these cells normally work and what happens in cases of jet lag, shift work, blindness, fever, aging and other conditions that appear to alter our daily schedules.

"We think that there is a master clock in the SCN, and many ‘slave’ clocks in the brain and body," Herzog said. "The ‘slave’ clocks may receive daily synchronizing signals from the master, but when they get out of phase, it takes several days to catch up. That very well may be happening with jet lag. It’s not the SCN that gets out of whack in a different environment – for instance, after flying to Paris – but other structures inside and outside of the brain."


Story Source:

The above story is based on materials provided by Washington University In St. Louis. Note: Materials may be edited for content and length.


Cite This Page:

Washington University In St. Louis. "Sleepless Aged Rats Show Biological Clock Problems." ScienceDaily. ScienceDaily, 14 August 2001. <www.sciencedaily.com/releases/2001/08/010814063122.htm>.
Washington University In St. Louis. (2001, August 14). Sleepless Aged Rats Show Biological Clock Problems. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2001/08/010814063122.htm
Washington University In St. Louis. "Sleepless Aged Rats Show Biological Clock Problems." ScienceDaily. www.sciencedaily.com/releases/2001/08/010814063122.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins