University of Alberta researchers have discovered spontaneously active receptors in the spinal cord
Bucking conventional knowledge, University of Alberta researchers have identified spontaneously active receptors in the spine that could be used to help treat victims of spinal cord injury.
David Bennett and Karim Fouad from the Faculty of Rehabilitation Medicine have discovered that the neurotransmitter serotonin, partially responsible for motor function, is not needed to activate receptors in the spinal column.
“These receptors, that serotonin activates normally in the spinal cord, become active on their own, spontaneously, many months after injury. Basically what it boils down to is the spinal cord wakes up on its own,” Bennett said.
The neurotransmitter serotonin is responsible for alertness and readies neurons in different parts of the body. With spinal injury, the cord is either severed or partially severed, so the neurotransmitter has no access to the receptors within.
This lack of access is part of the reason for paralysis. Bennett described it as having a spinal cord that is asleep.
Typically, the idea has been that without chemical access to receptors, they became inactive. But the U of A team has shown that this is not the case. With the discovery of spontaneously active receptors, the team sees several valuable applications.
The first is that this knowledge can be used to develop a potential treatment plan for injuries to restore some motor function or movement.
“The spinal cord is in this wakeful state ready to go. All it takes is even a small amount of residual descending connections to trigger walking movements or other motor functions,” Bennett said.
He added that the best way to utilize these residual connections is through physical therapy.
“Of course, since you have a spinal cord injury, the functions are never going to be perfect, but with training those people can learn to reuse this residual function,” Bennett said. “You basically have to relearn all these functions like walking, but it’s surprising how much training can help that.”
In addition to training, there are drugs called selective serotonin reuptake inhibitors that could help enhance residual connection when desired.
However, permanent wakefulness of the spinal cord is often undesired; this can contribute to muscle spasms, which is a major problem among paralysis patients that is not easily solved by typical anti-spastic drugs.
“Your spinal cord is in a permanent wakeful state and it’s also not very well-controlled from the brain. So, if you have someone with spinal cord injury and you pinch the skin or some sort of sensory input that comes to the spinal cord, you can trigger uncontrolled movements or spasms.”
But Bennett says that they can apply their discovery to find more effective drugs to treat spasms. His team has been examining cyproheptadine, an antihistamine that may block serotonin receptors, and they plan to continue with this research.
Bennett added that the discovery is exciting because it was so unexpected.
“It’s a bizarre thing where the receptor turns on without there being a transmitter or a chemical, and that hasn’t ever been shown in the spinal cord before. That concept is really a unique concept.”
Alexandria Eldridge, Senior News Editor