Paralyzed rats learn to walk again
UCLA scientists have made paralyzed rats walk again after spinal-cord injuries, in an achievement that could give hope to paraplegic people.
The findings suggest that severed nerve fibers do not have to regenerate for paraplegic rats to learn to walk again.
"The spinal cord contains nerve circuits that can generate rhythmic activity without input from the brain to drive the hind leg muscles in a way that resembles walking called 'stepping,'" explained principal investigator Reggie Edgerton of UCLA.
"Previous studies have tried to tap into this circuitry to help victims of spinal cord injury. While other researchers have elicited similar leg movements in people with complete spinal injuries, they have not achieved full weight-bearing and sustained stepping as we have in our study."
Edgerton's team tested rats with complete spinal injuries that left no voluntary movement in their hind legs. The rats were placed on a moving treadmill belt and given drugs that act on the neurotransmitter serotonin, along with low levels of electrical currents to the spinal cord below the point of injury.
The combination of stimulation and sensation triggered the spinal rhythm-generating circuitry and prompted walking motion in the rats' paralyzed hind legs.
After several weeks' training, the rats regained full weight-bearing walking, even managing to run and go backwards and sideways. Unfortunately, the injury still interrupted the brain's connection to the spinal cord-based rhythmic walking circuitry, meaning the rats couldn't actually walk of their own accord.
However, the authors are hopeful that neuro-prosthetic devices could help in humans.
The details will be published in the online edition of Nature Neuroscience.