Recalling painful memories while under the influence of the drug metyrapone reduces the brain's ability to re-record the negative emotions associated with them, according to a study published in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism. The study by a team of University of Montreal researchers at the Centre for Studies on Human Stress of Louis-H. Lafontaine Hospital challenges the theory that memories cannot be modified once they are stored in the brain.

"Metyrapone is a drug that significantly decreases the levels of cortisol, a stress hormone that is involved in memory recall," explained lead author Marie-France Marin. Manipulating cortisol close to the time of forming new memories can decrease the negative emotions that may be associated with them. "The results show that when we decrease stress hormone levels at the time of recall of a negative event, we can impair the memory for this negative event with a long-lasting effect," said Dr. Sonia Lupien, who directed the research.

Thirty-three men participated in the study, which involved learning a story composed of neutral and negative events. Three days later, they were divided into three groups - participants in the first group received a single dose of metyrapone, the second received double, while the third were given placebo. They were then asked to remember the story. Their memory performance was then evaluated again four days later, once the drug had cleared out.. "We found that the men in the group who received two doses of metyrapone were impaired when retrieving the negative events of the story, while they showed no impairment recalling the neutral parts of the story," Marin explained. "We were surprised that the decreased memory of negative information was still present once cortisol levels had returned to normal."

The research offers hope to people suffering from syndromes such as post-traumatic stress disorder. "Our findings may help people deal with traumatic events by offering them the opportunity to 'write-over' the emotional part of their memories during therapy," Marin said. One major hurdle, however, is the fact that metyrapone is no longer commercially produced. Nevertheless, the findings are very promising in terms of future clinical treatments. "Other drugs also decrease cortisol levels, and further studies with these compounds will enable us to gain a better understanding of the brain mechanisms involved in the modulation of negative memories."

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About the researchers

Marie-France Marin

Doctoral student

Centre for Studies on Human Stress of Louis-H. Lafontaine Hospital

Fernand-Seguin Research Centre of Louis-H. Lafontaine Hospital

University of Montreal's Department of Physiology

Doctoral scholarship, Canadian Institutes of Health Research (CIHR)

Dr. Sonia Lupien

Director, Centre for Studies on Human Stress of Louis-H. Lafontaine Hospital

Director, Fernand-Seguin Research Centre of Louis-H. Lafontaine Hospital

Full Professor, University of Montreal's Department of Psychiatry

Senior Investigator, CIHR Research Chair on Mental Health in Men and Women.

About the study

The University of Montreal is officially known as Université de Montréal. The study received funding from the Canadian Institutes for Health Research and has been published online in the Journal of Clinical Endocrinology & Metabolism.