The physical training began on a treadmill, with the 17 rats using a robotic harnessâ€”created especially for the studyâ€”that suspended the animals upright but did not propel them forward.
“Imagine you can’t get any signals from your brain to below the injuryâ€”you can still walk on a treadmill,” said Kleitman, who wasn’t part of the new study.
“The treadmill is dragging my right foot behind me,” she added. “That will stimulate a reflex in my left leg that will make my left leg take a step.”
Anything for Chocolate?
In addition to the treadmill therapy, the trained rats received mild electrical stimulationâ€”designed to mimic the signals the brain sends to move the legsâ€”and injections of chemicals known to help nerve cells, which carry those signals, to better communicate.
After three weeks of treadmill training, 10 of the 17 rats were encouraged to take steps on a sort of tiny runwayâ€”still in the harnesses, though, and still being electrochemically stimulated.
Within a few more weeksâ€”and with the incentive of a bit of chocolate at the end of the courseâ€”the runway rats were “sprinting” up stairs in their harnesses, study co-author Courtine said in a statement.
Though the rats still couldn’t walk unaided, they had undergone a “nearly complete” regrowth of spinal nerve fibers, reestablishing the severed connections between brain and haunches, the study says.
Hope for People?
All these treatments are already being tested in people, NIH’s Kleitman said. What makes the study exciting is that the methods have never before been tried in combination.
The electrochemical cocktail, she said, is what “to me, made this paper quite relevant, even though it’s just in rats.”
Mayo Clinic neurologistÂ Tony WindebankÂ agreed. “All the things they are doing in rats are things you can do in people.”
He cautioned, however, that stimulating and enhancing the automatic walking reflex is “much easier to do in quadrupeds compared to upright animals.”
But, he said, “I think it’s an important step forward,” even if “it’s not the giant step for mankindâ€”it’s not going to translate to, Let’s do this in people next month and have them walking.”
Kleitman believes the severity of the rats’ paralysis and subsequent recovery should give some people hope.
“Some people might say it’s not worth doing anything with” severely paralyzed people, “because there’s almost nothing left,” she said. “Studies like this one show it’s worth trying.”