Mice genetically engineered to overproduce the brain chemical serotonin died at an early age after developing symptoms similar to those of sudden infant death syndrome, suggesting improper regulation of serotonin may cause SIDS in humans.
Most of the mice died after being unable to regulate their heart rate and body temperature, scientists reported Friday in the journal Science.
Dr. Cornelius Gross, a study author and head of the project at the European Molecular Biology Laboratory in Monterotondo, Italy, said the work might prompt clinical research "to devise diagnostic tests to try to identify those kids most likely to . . . die of SIDS."
SIDS is a condition in which seemingly healthy babies between 1 month and 1 year old die without warning or explanation. It kills approximately 2,700 infants in the U.S. each year.
The mice were part of a study on serotonin's role in aggression and anxiety, but after they began dying, a scientist suggested the deaths might be related to SIDS.
"This was a chance discovery," Gross said.
Serotonin, in addition to affecting mood, regulates bodily functions such as temperature, respiration and heart rate.
The findings support autopsy-based results reported from 2006 in which researchers from Children's Hospital Boston, led by Dr. Hannah Kinney, found that infants who died of SIDS had abnormal serotonin-producing cells in their brain stems.
Although differences exist between the mice and babies who die of SIDS, both reports point to improper regulation of the serotonin system as a cause of the disorder, the researchers said.
"The main impact is if you produce a very specific deficit in the serotonin system, you get a disastrous result," said Dr. Gene Nattie, a professor of physiology at Dartmouth Medical School, who worked with Kinney. "That's why the paper is important. It's certainly a big step forward."