Researchers make paralyzed rats walk through a mix of chemical stimulation and structured physical therapy; only a little regrowth in the spine occurs, but the lower spinal column can take over some of the lost functionality under the right circumstances: "a severed section of the spinal cord can make a comeback when its own innate intelligence and regenerative capacity is awakened. ... After a couple of weeks of neurorehabilitation with a combination of a robotic harness and electrical-chemical stimulation, our rats are not only voluntarily initiating a walking gait, but they are soon sprinting, climbing up stairs and avoiding obstacles when stimulated. ... until now the spinal cord expressed so little plasticity after severe injury that recovery was impossible. ... under certain conditions, plasticity and recovery can take place in these severe cases - but only if the dormant spinal column is first woken up. To do this, [researchers] injected a chemical solution of monoamine agonists into the rats. These chemicals trigger cell responses by binding to specific dopamine, adrenaline, and serotonin receptors located on the spinal neurons. This cocktail replaces neurotransmitters released by brainstem pathways in healthy subjects and acts to excite neurons and ready them to coordinate lower body movement when the time is right. ... Five to 10 minutes after the injection, the scientists electrically stimulated the spinal cord with electrodes implanted in the outermost layer of the spinal canal, called the epidural space. ... a stimulated rat spinal column - physically isolated from the brain from the lesion down - developed in a surprising way: It started taking over the task of modulating leg movement, allowing previously paralyzed animals to walk over treadmills. These experiments revealed that the movement of the treadmill created sensory feedback that initiated walking - the innate intelligence of the spinal column took over, and walking essentially occurred without any input from the rat's actual brain. This surprised the researchers and led them to believe that only a very weak signal from the brain was needed for the animals to initiate movement of their own volition. ... newly formed fibers bypassed the original spinal lesion and allowed signals from the brain to reach the electrochemically-awakened spine. And the signal was sufficiently strong to initiate movement over ground."

Link: http://www.sciencedaily.com/releases/2012/05/120531145714.htm

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