Scientists make paralysed rats run again

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Scientists make paralysed rats run again

Sun Sep 20, 3:21 PM

PARIS (AFP) - Paralysed rats whose spinal cords had been severed from

their brains were made to run again using a technique that scientists

say can work for people, according to a study released Sunday.

Consistent electrical stimulation and drugs enabled the rats to walk on

their hind legs on a treadmill -- bearing the full weight of the body --

within a week of being paralysed.

With the addition of physical therapy, the rodents were able after

several weeks to walk and run without stumbling for up to 30 minutes,

reported the study, published in the journal Nature Neuroscience.

Remarkably, the animals could adjust their movements in response to

stimuli despite the lack of signals to and from the brain: when the

treadmill was reversed, for example, the rats walked backwards.

" This means that the spinal network is almost capable of cognitive

processing, " explained Gregoire Courtine, a professor at Zurich

University.

" It can understand that the external world is changing, and interpret

this information to modify the way it activates muscle, " he told AFP by

phone.

Earlier studies had shown that nerve networks in the spinal cord can

produce limited motion in the muscles independent of the brain or

sensory organs.

But this is the first time that researchers have been able to restore

normal or nearly normal functions.

" We can optimise the use of the circuitry in the spinal cord to the

point where the animals can sustain full weight-bearing locomotion, "

said Courtine.

" In some cases they actually walked with more consistent locomotive

patterns than non-injured animals. "

The next step is to develop devices that can be implanted inside the

body.

" We are now designing neuro-prostheses, arrays of electrodes that fit

like a second skin between the vertebrae and the spinal cord, " Courtine

explained.

A strip measuring three centimetres (1.2 inches) long and one hundredth

of a centimetre thick, the device is described as " minimally invasive "

because it does not penetrate into the spinal cord.

Courtine and colleagues are currently testing the neuro-prostheses on

rats, and expect to have an interface for humans within four years.

The new technique is designed to help patients with incomplete but

severe injuries, such as those who cannot walk independently.

" For these people, it is highly likely that this approach will improve

their function, " he said.

The mix of electrical stimulation and physical therapy may be enough to

restore significant mobility in many patients, but the addition of drugs

" would be extremely beneficial, " he added.

In the rat experiments, the researchers injected so-called serotonergic

agonists, a compound that mimics the effect of the neurotransmitter

serotonin and activates receptors in the central and peripheral nervous

system.

There are approximately a quarter of a million persons with serious

spinal cord injuries in the United States, according to the Foundation

for Spinal Cord Injury, Prevention, Care and Cure. Other sources

estimate the total worldwide at 2.5 million.

Nearly half of all spinal cord injuries are caused by automobile

accidents, and more than half occur among young people between 16 and 30

years old.