The scientists have developed a strain of mice in which it is possible to selectively shut down their brain serotonin-producing cells, which control breathing, temperature regulation and mood. When the serotonin cells were turned down, the animals failed to step up their breathing in response to an increase of the carbon dioxide levels in the air and their body temperatures dropped to match the air temperature.
The study has implications for understanding SIDS, which is linked to low serotonin levels and is believed to involve abnormalities in breathing and temperature control.
The scientists, including postdoctoral fellows Russell Ray and Andrea Corcoran, and student Rachael Brust, were able to turn down the serotonin levels in the mice using a new genetic technique in which receptors were inserted into serotonin neurons in the brain and those receptors were activated with a drug given while the animals were awake.
“The techniques used previously to study these neurons were more invasive, required the use of anesthesia, or involved knocking out a gene, each of which caused problems when interpreting the results,” explained George Richerson, M.D., Ph.D., professor and head of the UI Department of Neurology, who led the Iowa portion of the research team.
“This technique represents a huge leap forward because serotonin neurons can now be inhibited after the receptors are activated by injection of a chemical in a behaving animal. This approach is also likely to be applicable to a broad range of other brain neurons. That is part of the power of the approach — it can be used to study the functions served by many different neurons, not just serotonergic neurons,” Richerson said.
Richerson said the new approach, applied in this case to serotonin neurons, is a much better tool for studying the portions of the brain that control breathing and body temperature. That may help researchers learn more about the possible causes of SIDS.
“SIDS is the leading cause of postneonatal death among infants. If we can determine which infants face a higher risk for SIDS, we can develop treatments that may help prevent such tragedies,” added Richerson.
The new technique can also be used to study a large variety of neurological and psychiatric disorders, such as depression, panic disorder, Parkinson’s disease, Alzheimer’s and epilepsy.
The research results appear in the current edition of Science.
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