Exercise can stimulate injured neurons to regenerate their axons

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Exercise can help brain healing process News-Medical.net 2-Jun-2004

Exercise can stimulate injured neurons to regenerate their axons, which

are the primary transmission lines of the nervous system, according to a

study published June 1 in the print edition of the Proceedings of the

National Academy of Sciences, and the last week of May in the early

online edition.

" Our experiments show that the nervous system responds to injury in the

same way that it responds to activity that creates or eliminates

connections needed for brain cells to communicate with one another, "

said Jeffery L. Twiss, head of Nemours neuroscience research lab and

corresponding author of the study, titled " Voluntary Exercise Increases

Axonal Regeneration From Sensory Neurons. "

" In time, our further understanding of the mechanisms behind this

process could aid research into new treatments for brain diseases that

affect the lives of millions of Americans, " Twiss said.

Neuronal activity enhances synaptic plasticity, with new connections

forming between frequently used neural pathways. The term " synaptic

plasticity " refers to the ability to maintain or improve synapse

function. Twiss' team and a group of researchers from UCLA, under the

leadership of Gómez-Pinilla, found that this plasticity can

affect the ability of nerves to regenerate.

Previous research from the UCLA laboratory of Gómez-Pinilla, professor

of neurosurgery and physiological science, has shown that following

exercise, neurotrophin levels increase in the brain and spinal cord.

Neurotrophins, growth factors that promote neuron survival, positively

regulate synaptic plasticity underlying high-order neural processes such

as learning and memory, and walking. This research clearly demonstrates

that managed physical activity can be a realistic therapy to promote

functional recovery after brain and spinal cord injury.

To investigate how exercise-induced changes in neurotrophins affect

synaptic plasticity, Twiss and Gómez-Pinilla's groups examined the

growth of sensory neurons from rats that had access to running wheels

for zero, three or seven days.

The researchers observed that sensory neurons grew longer neurites, a

type of extension, when cultured from animals that had exercised,

compared to sedentary animals. Neurite length correlated directly with

the distance that animals ran.

To determine whether exercise could also enhance axon regeneration

within a living organism, the researchers crushed the sciatic nerve of

animals that had exercised for seven days prior to the injury.

Significantly more sciatic nerve axons regenerated in the exercised

animals than the sedentary animals. Injecting an inhibitor of

neurotrophin receptor activity into neurons prior to exercise blocked

the activity-induced axon growth.

According to researchers, these results indicate that physical activity

may alter synaptic plasticity and regenerative capacity through

neurotrophin signaling mechanisms.

" There is much work to be done, but we hope to take advantage of the

molecular changes seen after exercise to optimize repair or regeneration

of the nervous system in the future, " Twiss said.

Nemours Biomedical Research, which owns and operates the Alfred I.

duPont Hospital, has a long-standing commitment to scholarly and

scientific endeavors directed towards improving the health of children.

For more information, please visit the Web site at www.nemours.org.