Now researchers at the European Molecular Biology Laboratory in Italy have revealed that an imbalance of the neuronal signal, serotonin, in the brainstem caused sudden death in mice, according to the study in Science magazine.

The brainstem, which is at the base of the brain and joins to the spinal cord, coordinates many of the body's vital functions such as the cardiovascular and respiratory systems.

The scientists modified serotonin systems in mice seeking to under stand the role of the molecule on transmitting neuron signals in the brainstem. Victims of Sudden Infant Death Syndrome (SIDS) have shown alterations in those brainstem neurons that communicate using the signaling molecule serotonin.

"At first sight the mice were normal. But then they suffered sporadic and unpredictable drops in heart rate and body temperature," said scientist Cornelius Gross.

"More than half of the mice eventually died of these crises during a restricted period of early life. It was at that point that we thought it might have something to do with SIDS."

Until now it had remained unclear how changes in serotonin signaling in the brainstem could be involved in cot deaths.

The findings showed that deficits in serotonin signaling in the brainstem can lead to sudden death and support the idea that a congenital serotonin defect could play a critical role in SIDS.

"We hope the mouse model will help identify risk factors for SIDS," said researcher Enrica Audero.

"One open question is whether like in SIDS, the animals die during sleep and whether we can identify which mice will die by looking at their heart rate or body temperature before the crisis. Ultimately, we hope it will give new ideas to doctors about how to diagnose babies at risk for SIDS." - AFP