NEW YORK (Reuters Health) - Even short but intense periods of stress may have long-term consequences on the physical functioning of the nerve cells in the brain, according to the results of a mouse study released on Thursday.

While much has been documented about people's various reactions to very stressful events, scientists are still unclear about the specific changes, if any, that occur on a cellular level in a person's brain.

Now, Dr. Hermona Soreq of The Hebrew University of Jerusalem in Israel and colleagues report that stress can alter the production of a protein in the brain required for normal nerve function, resulting in lingering oversensitivity to outside stimuli. The finding may shed light on how stress can produce long-term problems, such as post-traumatic stress disorder.

Specifically, the investigators found that exposure to stress caused messenger ribonucleic acid (mRNA)--the cell's machinery that helps translate DNA into the proteins essential for normal functioning of the body--to produce a slightly different version of a key protein needed for normal nerve cell function. The brain chemical, acetylcholinesterase (AChE), helps control the flow of signals between nerve cells.

Soreq and her team conducted studies on live mice and cultured mouse brain cells and found that stress could cause an alternate form of AChE to form. The alternate form, AChE-R, is a rarely found version of the chemical and seemed to cause nerve cells to become hypersensitive to neurotransmitters in the brain for several weeks after exposure to stress. The findings are published in the January 18th issue of the journal Science.

It is not yet clear if the results are applicable to stressed-out humans, Soreq noted.

``The study was performed in mice, which is important to keep in mind,'' Soreq told Reuters Health. ``But it was designed based on symptoms reported by post-trauma patients: drastic reactions to relatively low drug doses, depression, difficulties in concentration, anxiety and inability to sleep,'' she added.

``Most of these can be explained by changes in (the brain's ability to transmit nerve impulses),'' Soreq stated.

One result of this study may be a rethinking of the drug dosages given to patients who have had traumatic experiences, particularly patients who are receiving drugs that affect the nervous system, she said.

SOURCE: Science 2002;295:508-512.

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