By Maureen Salamon
THURSDAY, May 31 (HealthDay News) -- In research that hints at new ways to tackle paralysis, a combination of drugs, electrical stimulation and "willpower-based training" prompted paralyzed rats to walk and even run.
But experts noted the treatment might not necessarily work in humans.
Researchers at the Swiss Federal Institute of Technology re-routed signals from the rats' brains to their spinal cords with chemical injections, electrodes and a chocolate reward that motivated them to walk voluntarily, supporting their entire weight on their hind legs.
"We expected that the rats would recover some degree of locomotor functions. We were, however, surprised about the extent of the recovery -- paralyzed rats were able to pass obstacles and run up stairs -- and the consistency with which we observed it," said study co-author Janine Heutschi, a doctoral student at the institute.
"Because the rats actively participate in the tasks, as opposed to automated movements, the brain is actively involved and is challenged to find new ways of controlling the hind limbs," she added. "Over time, new nerve connections are then formed."
The study findings are published in the June 1 issue of the journal Science.
About half of human spinal cord injuries lead to paralysis, which can be complete or partial. While the brain and spinal cord can often adapt and recover from moderate injury through a quality known as neuroplasticity, severe injuries can preclude recovery, the study authors noted.
In the new research, begun five years ago at the University of Zurich in Switzerland, rats with severed spinal cords were injected with chemicals known as monoamine agonists that replace the neurotransmitters dopamine, adrenaline and serotonin, which are released from the brains of healthy individuals to help coordinate lower body movement. About 10 minutes later, the researchers electrically stimulated the spinal cords with electrodes implanted near the spinal canal, leaving the rats to initiate leg movement after being motivated by chocolate.
A harness that robotically supported the rats' back legs -- kicking in only when they lost balance -- gave them the impression of having a healthy spinal column, the study authors said, and that translated into a fourfold increase in nerve fibers throughout the brain and spine.
"Over the past 20 years or so, research has moved away from getting damaged [nerve] pathways to work and trying to recruit other pathways to work -- to trick the spinal cord into creating a detour or other routes," explained Dr. Nathaniel Tindel, an attending orthopedic spinal surgeon at Lenox Hill Hospital in New York City. "That's the essence of this research. It's not groundbreaking in this sense, but what is unique is not that they got rats to move, but the techniques and protocol they used. This is great stuff because it's really delineating an approach for studying these new pathways."
Dr. Robert Grossman, chairman of neurosurgery at Methodist Neurological Institute in Houston, noted that the new study builds on a recently published case where a paralyzed young man regained standing and some voluntary leg movements after he was trained on a treadmill using electrical stimulation.
This new study is "a significant contribution to understanding the biological mechanisms underlying the generation of [movement] due to spinal cord injury," he said.
Heutschi said clinical trials to test the therapy on humans are being planned, though "we don't know yet what we can expect from studies with human patients."
But Tindel cautioned that the treatment methods used in this research aren't practical in humans because "rats have a phenomenal ability to regenerate, better than we do."
"It's a nice model because they can get results quicker," Tindel said, "but rats have a different system."
The U.S. National Library of Medicine has more information about paralysis.
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