SUNDAY, Sept. 20 (HealthDay News).
A three-pronged approach to treating spinal cord injuries allowed paralyzed
rats to walk without receiving signals from the brain, scientists report.
Spinal cord injuries result in paralysis when the nerve fibers that carry
information to and from the brain are damaged or severed. Much of the focus
of research into spinal cord injuries has been exploring ways of
regenerating those nerve fibers and connections, which has so far met with
limited success in people.
In the new study, rats were treated with a combination of drugs, electrical
stimulation of the spinal cord and locomotor training, a rehabilitation
technique. The combined treatment enabled the rats to walk with a
near-normal gait on a treadmill, without the muscles receiving signals from
"The study demonstrates that the lower spinal cord has circuitry that is
sufficient to support virtually normal, weight-bearing locomotion," said
senior study author V. Reggie Edgerton, a professor of physiological
sciences and neurobiology at the University of California, Los Angeles.
The study appears in the Sept. 20 online edition of Nature Neuroscience.
Previous research has been able to coax a stepping motion using one or two
of those techniques, said Susan Howley, executive vice president of research
for the Christopher & Dana Reeve Foundation, which provided some funding for
the current research. But this is the first study to achieve actual
weight-bearing walking, as opposed to the motions of walking.
"The thing that's very exciting about this is that for the first time they
actually showed they can get these rats, with no input from the brain, to
step near normally," Howley said. "On the treadmill, they were able to bear
weight and step virtually as well as they had been prior to the injury.
That's a remarkable achievement."
In the study, researchers put rats whose lower legs were paralyzed in a
harness on a slow-moving treadmill and gave them a drug called quipazine, a
serotonin agonist that enhances the function of the spinal nerve circuitry.
The researchers then used an epidural to apply electrical currents to the
dura of the spinal cord, the protective membrane that surrounds it, below
the point of injury.
The combination of drugs and electrical stimulation caused the rats to begin
walking. Several weeks of daily locomotor training on the treadmill enabled
near-normal weight-bearing walking -- including backward, sideways and
Because the brain was still unable to direct the walking, the rats could
only walk when hooked up to electrical stimulation on the treadmill.
Previous studies have shown that the nerve circuitry of the spinal cord is
able to generate rhythmic activity that can direct leg muscles to step, the
researchers said. With the right input, the nerves can learn to interpret
sensory information from the stepping motion even without help from the
"Previous research has shown the spinal cord can learn whatever task it's
being trained to do," Edgerton said. "The spinal cord can interpret the
sensory information associated with the stepping, respond to that sensory
information and sustain the stepping based on the sensory information."
Locomotive training is a rehabilitation technique that uses that concept to
retrain the spinal cord circuitry after injury. Widely used in some European
countries, locomotor training involves placing people with spinal cord
injuries in harnesses while physical therapists move their legs in a walking
People who undergo locomotor training often see improvements in respiration,
bladder function, blood sugar levels and circulation below the level of the
lesion, which can help prevent the skin breakdown that can occur as a result
of paralysis, Howley said. Others even recover trunk stability, which can
enable them to move from a bed to a wheelchair, or a wheelchair to a car,
Though a treatment using the three-pronged approach is at least several
years away, the study suggests the potential of using neuroprosthetic
devices to activate spinal cord rhythmic circuitry, said study author
Gregoire Courtine, a professor in the department of neurology at the
University of Zurich in Switzerland. His team is currently developing a
device that they hope to begin testing in small clinical trials in three to
About 5.6 million Americans, or one in 50, has some level of paralysis,
according to a survey released in April of 33,000 U.S. households by the
Christopher & Dana Reeve Foundation. About one-quarter of the nearly 2
percent of the U.S. population living with paralysis is due to a spinal cord
Susan Howley, executive vice president, research, Christopher & Dana Reeve
Foundation, Short Hills, N.J.; V. Reggie Edgerton, Ph.D., professor,
physiological sciences and neurobiology, University of California, Los
Angeles; Gregoire Courtine, professor, University of Zurich, Switzerland;
Sept. 20, 2010, Nature Neuroscience, online.