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Serotonin Levels May Play Role in Sudden Infant Death

Mice with abnormal levels have drops in heart rate and body temperature, and die soon after birth

MONDAY, July 7 (HealthDay News) -- Abnormalities in serotonin balance in mice can lead to drops in heart rate and body temperature, and death within months of birth, and the findings may aid research on sudden infant death syndrome (SIDS), according to the results of a study published in the July 4 issue of Science.

Enrica Audero, from the European Molecular Biology Laboratory in Monterotondo, Italy, and colleagues engineered mice who could be triggered to overproduce serotonin receptor 1A (Htr1a) in the raphe nuclei, an area of the brain found to have abnormalities in serotonin neurons and decreases in Htr1a and serotonin transporter in SIDS cases.

The researchers found that most of the mice died before 3 months of age, most frequently between postnatal days 25 and 80. Only 30 percent survived beyond 120 days. Overexpressing Htr1a at later developmental times reduced the death rate. The mice produced increased levels of serotonin compared with normal mice, with further reduced serotonin neuronal activity (autoinhibition), and had sporadic autonomic crises characterized by drops in heart rate and body temperature.

"These findings show that excessive serotonin autoinhibition is a risk factor for catastrophic autonomic dysregulation and provide a mechanism for a role of altered serotonin homeostasis in sudden infant death syndrome," Audero and colleagues conclude.

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