In a study published in the Dec. 14, 2005, issue of the Journal of Neuroscience, the researchers describe in a mouse model for RS the source of erratic breathing, which has important implications for children with RS.
Along with breathing problems, RS causes slowed brain and head growth, mental retardation, seizures, gait abnormalities and handwringing.
"It is absolutely tragic for the family," said Jan-Marino Ramirez, professor of organismal biology and anatomy at Chicago and lead author of the paper. "It's a progressive disease that shows no mercy."
In order to study the breathing pattern more closely, Ramirez and his team showed that mice with the RS gene exhibit the same behavior as children: They breathe irregularly and stop breathing often.
According to Ramirez, one hypothesis that has dominated the thinking of many clinicians is that the erratic breathing is due to cortical problems. "It's as if they want to stop breathing," he said. "Some clinicians went that far to suggest that it could be pleasurable for the child to stop breathing all of the time because they get a euphoric high. Or they do this because they're agitated."
However, the researchers traced the problem not to the cortex but to the breathing center itself--in the medulla. The researchers isolated the breathing center from mutant mice and were able to demonstrate that the same erratic breathing pattern, which is so characteristic for RS, also was expressed in the isolated brain tissue, revealing the breathing center as the source of the problem.
They also found, specifically in the breathing center, a significantly decreased amount of the neuromodulator norepinephrine.