THURSDAY, July 3 (HealthDay News) -- A malfunction in the
regulation of the brain chemical serotonin may be at the root of
sudden infant death syndrome (SIDS), new research suggests.
Reporting in the July 4 issue of
Science, Italian researchers explain how alterations in
normal serotonin levels in a mouse model resulted in sudden death
for many of the mice. And, just prior to death, the mice
experienced changes in their heart rate and their temperature that
were similar to the changes suspected to occur in SIDS.
"This mouse model is important. Causing dysfunction in brainstem
serotonin can lead to death in a majority of affected animals,"
Marian Willinger, a SIDS expert with the U.S. National Institute of
Child Health and Human Development, said at a press conference
Thursday. She added that the severe cardiac and thermal regulation
changes that occurred in the mice are similar to risk factors
associated with SIDS. For example, she said, stomach sleeping is
more likely to cause heart rate variability than back sleeping.
Over-bundling babies, and thus overheating them, is also a known
risk factor for SIDS, she said.
The Italian researchers didn't set out to develop a mouse model
of SIDS; they were originally looking at the serotonin system and
how the body maintains its levels of the important
neurotransmitter. But when many of the mice unexpectedly died, a
scientist who was involved with SIDS research pointed out the
similarities.
The brain's serotonin system works similar to a home thermostat,
study author Cornelius Gross, from the European Molecular Biology
Laboratory in Monterotondo, Italy, explained at the press
conference. "When the heat rises past a set point, the heating is
shut off. Serotonin has the same type of feedback," he noted.
The mouse model developed by Gross and his colleagues
essentially contains a switch that they can turn on and off. This
switch tells the mouse body to overexpress a serotonin receptor. In
turn, that causes negative feedback that tells the mouse brain to
reduce serotonin levels.
Serotonin is a neurotransmitter -- a chemical messenger -- that
helps the brainstem communicate with nerve cells in the spinal cord
and beyond. It is involved in many critical body functions, such as
heart rate regulation, breathing, temperature regulation and
more.
Interestingly, a complete block of serotonin doesn't cause
death. "Having a dysfunction in the serotonin system is somehow
worse than having no serotonin at all," Gross said.
These findings could lead to new ways to identify which babies
are at the greatest risk of SIDS, said Gross. Both Gross and
Willinger said they don't foresee a time when a pharmacological
intervention could be developed to prevent SIDS, however.
"Drug therapy is probably not the way to do this. These
neurotransmitters control a huge number of functions," said
Willinger.
But, "if you could identify which babies are at risk, you could
be a little more specific in who you insist make behavioral changes
and modifications," said Dr. Rachel Moon, a pediatrician and SIDS
researcher at Children's National Medical Center in Washington,
D.C.
"Some babies are more at risk, and these environmental factors
could overwhelm the baby's capabilities," added Moon, who is also a
member of the American Academy of Pediatrics' SIDS Task Force.
More information
To learn more about preventing SIDS, visit the
U.S. National Institute of Child Health and Human
Development.
