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Finding could explain age-related decline in motor function

Posted on Thursday, February 06, 2014 · Volume: XLVII · Issue: 3


Ben Eaton, Ph.D., assistant professor of physiology, and graduate student Rebekah Mahoney are authors of a study that offers clues as to why muscles weaken with age.
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Ben Eaton, Ph.D., assistant professor of physiology, and graduate student Rebekah Mahoney are authors of a study that offers clues as to why muscles weaken with age. clear graphic

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Contact: Will Sansom, 210-567-2579

SAN ANTONIO (Feb. 5, 2014) — Scientists from the School of Medicine at the UT Health Science Center San Antonio have found a clue as to why muscles weaken with age.

In a study published Feb. 5 in The Journal of Neuroscience, they report the first evidence that “set points” in the nervous system are not inalterably determined during development but instead can be reset with age. They observed a change in set point that resulted in significantly diminished motor function in aging fruit flies.

Set points determine stable functions in the body
“The body has a set point for temperature (98.6 degrees), a set point for salt level in the blood, and other homeostatic (steady-state) set points that are important for maintaining stable functions throughout life,” said study senior author Ben Eaton, Ph.D., assistant professor of physiology at the Health Science Center. “Evidence also points to the existence of set points in the nervous system, but it has never been observed that they change, until now.”

New set point observed
Dr. Eaton and lead author Rebekah Mahoney, a graduate student, recorded changes in the neuromuscular junction synapses of aging fruit flies. These synapses are spaces where neurons exchange electrical signals to enable motor functions such as walking and smiling. “We observed a change in the synapse, indicating that the homeostatic mechanism had adjusted to maintain a new set point in the older animal,” Mahoney said.

The change was nearly 200 percent, and the researchers predicted that it would leave muscles more vulnerable to exhaustion.

Aside from impairing movement in aging animals, a new functional set point in neuromuscular junctions could put the synapse at risk for developing neurodegeneration — the hallmark of disorders such as Alzheimer’s and Parkinson’s diseases, Mahoney said.

Video:
Watch 7 days old videoVideo:
Watch 42 days old video

These videos show the differences in motor function between young and old fruit flies (7 days old and 42 days old, respectively). The activity of the legs is significantly diminished in the older fly as is the extension of the proboscis, the body part that is used to suck up food and water.
clear graphic
Video: Watch 7 days old video
Video: Watch 42 days old video
These videos show the differences in motor function between young and old fruit flies (7 days old and 42 days old, respectively). The activity of the legs is significantly diminished in the older fly as is the extension of the proboscis, the body part that is used to suck up food and water.
clear graphic

 


New therapies for the future
“Observing a change in the set point in synapses alters our paradigms about how we think age affects the function of the nervous system,” she said.

It appears that a similar change could lead to effects on learning and memory in old age. An understanding of this phenomenon would be invaluable and could lead to development of novel therapies for those issues, as well.

Joel Rawson, Ph.D., of the University of Alaska at Anchorage, formerly a postdoctoral fellow in Dr. Eaton’s lab, is a study co-author.

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The University of Texas Health Science Center at San Antonio, one of the country’s leading health sciences universities, ranks in the top 3 percent of all institutions worldwide receiving National Institutes of Health funding. The university’s schools of medicine, nursing, dentistry, health professions and graduate biomedical sciences have produced more than 29,000 graduates. The $765.2 million operating budget supports eight campuses in San Antonio, Laredo, Harlingen and Edinburg. For more information on the many ways “We make lives better®,” visit www.uthscsa.edu.

 
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