Featured Research

from universities, journals, and other organizations

Depression Model Leaves Mice With Molecular Scar

Date:
February 28, 2006
Source:
NIH/National Institute of Mental Health
Summary:
Repeated defeat by dominant animals leaves a mouse with an enduring "molecular scar" in its brain that could help to explain why depression is so difficult to cure. Silencer molecules turned off a gene for a key protein in the brain's hippocampus. Antidepressants compensated for the resulting social avoidance syndrome, but failed to remove the silencers, which are thought to remain as a latent source of vulnerability to future depression-like responses to stress.

In addition to triggering a depression-like social withdrawal syndrome, repeated defeat by dominant animals leaves a mouse with an enduring "molecular scar" in its brain that could help to explain why depression is so difficult to cure, suggest researchers funded by the National Institutes of Health's (NIH) National Institute of Mental Health (NIMH).

Related Articles


In mice exposed to this animal model of depression, silencer molecules turned off a gene for a key protein in the brain's hippocampus. By activating a compensatory mechanism, an antidepressant temporarily restored the animals' sociability and the protein's expression, but it failed to remove the silencers. A true cure for depression would likely have to target this persistent stress-induced scar, say the researchers, led by Eric Nestler, M.D., The University of Texas Southwestern Medical Center, who report on their findings online in Nature Neuroscience during the week of February 26, 2005.

"Our study provides insight into how chronic stress triggers changes in the brain that are much more long-lived than the effects of existing antidepressants," explained Nestler.

Mice exposed to aggression by a different dominant mouse daily for 10 days became socially defeated; they vigorously avoided other mice, even weeks later. Expression of a representative gene in the hippocampus, a memory hub implicated in depression, plummeted three-fold and remained suppressed for weeks. However, chronic treatment with an antidepressant (the tricyclic imipramine) restored expression of the gene for brain derived neurotrophic factor (BDNF) to normal levels and reversed the social withdrawal behavior. BDNF in the hippocampus has been linked to memory, learning and depression, but Nestler said social defeat stress probably similarly affects other genes there as well.

The researchers pinpointed how social defeat changes the BDNF gene's internal machinery. They traced the gene expression changes to long-lasting modifications in histones, proteins that regulate the turning on-and-off of genes via a process called methylation. Methyl groups, the silencer molecules, attach themselves to the histones, turning off the gene. Notably, imipramine was unable to remove these silencer molecules, suggesting that they remained a latent source of vulnerability to future depression-like responses to stress.

Imipramine reversed the suppressed BDNF gene expression by triggering a compensatory mechanism, acetylation, in which molecular activators attach themselves to the gene and overcome the silencer molecules. Imipramine turned off an enzyme (Hdac5) that degrades the activators, allowing them to accumulate.

"The molecular scar induced by chronic stress in the hippocampus, and perhaps elsewhere in the brain, can't be easily reversed," said Nestler. "To really cure depression, we probably need to find new treatments that can remove the silencer molecules."

###

Tsankova NM, Berton O, Renthal W, Kumar A, Neve R, Nestler EJ. Sustained hippocampal chromatin regulation in a mouse model of depression and antidepressant action. Nature Neuroscience. Published online, 2/26/2006.

NIMH is part of the National Institutes of Health (NIH), the Federal Government's primary agency for biomedical and behavioral research. NIH is a component of the U.S. Department of Health and Human Services.


Story Source:

The above story is based on materials provided by NIH/National Institute of Mental Health. Note: Materials may be edited for content and length.


Cite This Page:

NIH/National Institute of Mental Health. "Depression Model Leaves Mice With Molecular Scar." ScienceDaily. ScienceDaily, 28 February 2006. <www.sciencedaily.com/releases/2006/02/060228180631.htm>.
NIH/National Institute of Mental Health. (2006, February 28). Depression Model Leaves Mice With Molecular Scar. ScienceDaily. Retrieved February 1, 2015 from www.sciencedaily.com/releases/2006/02/060228180631.htm
NIH/National Institute of Mental Health. "Depression Model Leaves Mice With Molecular Scar." ScienceDaily. www.sciencedaily.com/releases/2006/02/060228180631.htm (accessed February 1, 2015).

Share This


More From ScienceDaily



More Mind & Brain News

Sunday, February 1, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NFL Concussions Down; Still on Parents' Minds

NFL Concussions Down; Still on Parents' Minds

AP (Jan. 30, 2015) The NFL announced this week that the number of game concussions dropped by a quarter over last season. Still, the dangers of the sport still weigh on players, and parents&apos; minds. (Jan. 30) Video provided by AP
Powered by NewsLook.com
Study Shows Newborn Chicks Count From Left to Right Just Like Humans

Study Shows Newborn Chicks Count From Left to Right Just Like Humans

Buzz60 (Jan. 30, 2015) Researchers for the first time identified human&apos;s innate preference for associating low and high numbers with the left and right respectively in another species. Jen Markham (@jenmarkham) explains. Video provided by Buzz60
Powered by NewsLook.com
Best Mood Elevating, Feel Good Shakes & Smoothies

Best Mood Elevating, Feel Good Shakes & Smoothies

Buzz60 (Jan. 30, 2015) You can elevate your mood by having a meal in a glass. Fitness and nutrition expert John Basedow (@JohnBasedow) offers the best &apos;feel good&apos; smoothies and shakes chock full of depression-relieving ingredients...including apples, berries, lemons, cucumbers, papaya, kiwi, spinach, kale, whey protein, matcha, ginger, turmeric and cinnamon. Video provided by Buzz60
Powered by NewsLook.com
Poll Says Firstborn Is Responsible, Youngest Is Funnier

Poll Says Firstborn Is Responsible, Youngest Is Funnier

Newsy (Jan. 30, 2015) According to a poll out of the U.K., eldest siblings feel more responsible and successful than their younger siblings. 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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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