Acute Stress Leaves Epigenetic Marks on the Hippocampus

http://www.sciencedaily.com/releases/2009/12/091231153341.htm

ScienceDaily (Jan. 4, 2010) — In trying to explain psychiatric disorders, genes simply cannot tell the whole story. The real answers are in the interaction of genes and the environment. Post-traumatic stress disorder requires some trauma, for instance, and people, for the most part, aren't born depressed. Now research has revealed one mechanism by which a stressful experience changes the way that genes are expressed in the rat brain. The discovery of "epigenetic" regulation of genes in the brain is helping change the way scientists think about psychiatric disorders and could open new avenues to treatment.

Richard Hunter, a postdoc in Rockefeller University's Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology, found that a single 30-minute episode of acute stress causes a rapid chemical change in DNA packaging proteins called histones in the rat hippocampus, which is a brain region known to be especially susceptible to the effects of stress in both rodents and humans.

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Hunter also checked for similar changes as a result of chronic stress -- exposure to a 30-minute stress each day for 21 days. He did not find a major effect, which could reflect the animals' adjusting to the stress. However, when he treated the rats with fluoxetine, the generic form of the popular antidepressant Prozac, he reversed some methylation effects associated with chronic stress.

It's becoming increasingly evident, Hunter says, that the epigenetic changes like the methyl marks he observed and others, such as acetylation and phosphorylation, could play a significant role in the brain's response to stress and the treatment of stress related diseases, such as post-traumatic stress disorder.

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