Individuals with spinal cord injury at the top of the spine (location C-3 or above) have a hard time breathing. The spinal cord injury, a lesion in the spine, prevents the brain from sending messages to the nerves that operate the diaphragm. As a result, the diaphragm has a difficult time working and therefore the individual has a hard breathing.
Most people with neurologically complete lesions above C-3 die before receiving medical treatment. Those who survive are usually dependent on mechanical respirators to breathe. (National Spinal Cord Injury Association: http://spinalcord.org/news.php?dep=17&page=94&list=1191).
Using a rat model, Jerry Silver, Ph.D, professor of neurosciences at Case Western Reserve University School of Medicine, performed a half lesion in the spinal cord at C-2, preventing the diaphragm from functioning on the side of the lesion. Knowing that Channelrhodopsin-2 (ChR2), a light sensitive protein, made neurons fire when exposed to light, he then injected a virus containing ChR2 into the spine between C-3 and C-6, just below the lesion.
"The nerve cells with ChR2 "think" they are photoreceptors," said Silver. "So by shining light on the nerve cells it pushes them to work."
After four days, Silver and his team exposed the spinal cord to light. First they tried continuous light and then moved on to experimenting with light pulses.
"We found that when we repeated five minutes of one second pulses of light followed by five minutes of rest—for three cycles—and then switching the light off, that there was a bizarre seizure followed by normal breathing," said Silver.
Both sides of the diaphragm worked in tandem and the blood was well oxygenated. Breathing lasted for a day and a half without additional light stimulation.
Silver said there are groups already working on minimally invasive light sources, eliminating the need to surgically expose the spinal cord. Meanwhile, Silver intends to apply this same technique to the bladder.
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