The current study appears in the November 1 Journal of the American Medical Association provides additional evidence that brainstem abnormalities may impair an infant's ability to sense high carbon dioxide and low oxygen levels. Such impairment would put an infant at risk in situations in which they breathe in their own exhaled breath, depriving them of oxygen. The study represents the latest in a body of research begun in the mid 1980's and initiated by study senior author, Hannah Kinney, .M.D. Dr. Kinney is a longtime grantee of the NICHD. In 1983, when she was a fellow in pathology, Dr. Kinney published a study describing subtle scarring on the brainstem of a number of infants who died of SIDS, corroborating isolated observations by other researchers at the time. During the 1990s, Dr. Kinney and her coworkers examined brainstem tissue from SIDS infants, comparing them to brainstem tissue from controls, to determine which of 6 neurotransmitter systems might potentially be involved in the disorder.
The researchers learned that a region at the surface of the brainstem using glutamate and acetylcholine-both neurotransmitters thought to be involved in sensing carbon dioxide levels in the blood-were abnormal in SIDS cases. However, the greatest involvement appeared to be with a wider brainstem network relying on the neurotransmitter serotonin, thought to play an even greater role in regulating breathing. Infants who died of SIDS appeared to have fewer serotonin receptors than did infants who died of other causes. At the time, multiple subtypes of the serotonin receptor had not yet been identified.
In the current study, Drs. Kinney, Paterson, and their colleagues took advantage of more refined methods to examine the pattern of the serotonin receptor 1A subtype. They were also able to count serotonin-using cells, and estimate their prevalence in the brainstem, something that had not been possible previously. In future studies, the researchers plan to examine the role of other serotonin receptor subtypes in both lab animals and in SIDS cases. Moreover, they are also planning to test selective serotonin reuptake inhibitors (SSRIs) in pregnant lab animals, to see if the drugs have an effect on the fetal animals' developing brainstems in regions that are affected in SIDS infants
"Our goal is to find a way-a diagnostic test-to identify these defects in living infants and then find a way to correct these defects by drugs or other means as the infant passes through the first six months of life, the period of greatest risk for SIDS," Dr. Kinney said.
Along with providing funding for Dr. Kinney's laboratory, the NICHD funds a wide range of research projects in sudden infant death syndrome. The Back to Sleep Campaign, which urges parents and caregivers to place infants to sleep on their backs, has greatly reduced the SIDS rate. However, the practice cannot eliminate all SIDS deaths.
"Back sleeping is an intervention for all babies, but we still can't target high risk babies because we can't identify them," said Marian Willinger, PhD. "There are still babies who die of SIDS after being placed on their backs."
The NICHD supports a broad portfolio of SIDS research, which includes research on the brain, biological and behavioral markers of abnormal brain function, along with research on prenatal, genetic, behavioral, and environmental factors that may increase SIDS risk. The NICHD also supports technology development to detect potential abnormalities in infants at risk for SIDS.
"Eventually, we hope to have an understanding of the developmental disease process underlying SIDS, so that we can identify infants at highest risk and provide them with appropriate intervention," Dr. Willinger said.
The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Web site at http://www.nichd.nih.gov/.
The National Institutes of Health (NIH) — The Nation's Medical Research Agency — includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical, and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.