Spring 2005 Table of Contents.
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 New & Now.

Stories:

Gain Without Pain

Packaged Corn

Sober Students

Deep Breathing

Bad Cat Teeth

Cellular Slowdown

Sensory Shopping

 

Deep Breathing

Whether we think about it or not, our breathing quickens when our muscles get active -- this thanks to neurons that tell our respiratory system to kick it up. But how, physiologically speaking, do muscle movements trigger this neural response? And why does it happen automatically?

Answers have long eluded researchers, but Jeffrey Potts, an MU associate professor of veterinary biomedical science and research investigator at the Dalton Cardiovascular Research Center, is closing in. The stakes are much higher than simply explaining why we huff and puff at the gym; unraveling this puzzle could lead to a clearer picture of a host of serious respiratory disorders, among them Sudden Infant Death Syndrome (SIDS), which claims the lives of 2,000 to 3,000 infants each year, and sleep apnea, an ailment affecting some 12 million American adults.

Researchers have long known that when people begin exercising, sensory neurons in skeletal muscles become active, sending signals to the spinal cord. But where they go from there was anybody's guess. Potts hypothesized that the signals travel either straight from the spinal cord to respiratory neurons in the medulla or else from the spinal cord to respiratory neurons in the pontine -- another area of the brainstem -- and then on to the medulla.

To determine which of these scenarios was most likely, Potts stimulated muscle movements in a group of laboratory rats. Right on cue, their breathing quickened. He next injected the rats with a drug that blocked neural transmissions in their pontines. Again he stimulated muscle movement. This time the increased muscle activity did not affect the rats' breathing rhythms.

"Neurons in the pontine respiratory group have long been known to play an important role in the timing of normal breathing patterns," Potts says. "However, our findings are the first to show that pontine neurons also play a crucial role in the timing of breathing rhythms during muscle movements associated with exercise."

Potts also identified multiple synaptic connections that make changes in breathing patterns. By learning more about transmissions along these pathways, scientists will be able to better understand how neural signal processing can go awry, as occurs in SIDS or sleep apnea. Potts' research is funded by the National Institutes of Health, the American Heart Association and the Children's Hospital of Michigan. His findings were published this spring in the Journal of Neuroscience.

       
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