Researchers in the University of Alberta's Faculty¹ of Rehabilitation² Medicine（康复医学） have made an important discovery that could lead to more effective treatments for spinal³-cord injuries. Karim Fouad and David Bennett have identified one of the body's natural self-repair mechanisms⁴ that kick in after injury. To help understand the discovery the researchers say it is important to first describe the neurons in the spinal cord that control muscle contractions⁵. These neurons（神经原） represent a fairly autonomous⁶ part of the nervous system that control many basic functions such as walking and bladder（膀胱） control. These neurons are brought into a state of readiness by a transmitter called serotonin（血清素） . Serotonin originates in the brain and projects down the spinal cord where it binds⁷ to serotonin receptors on the neurons. This process turns a quiet neuron into one that's ready to respond to fast inputs⁸ from the brain.

When someone suffers a spinal-cord injury they can lose almost all serotonin projections⁹, so it was previously¹⁰ thought that the serotonin receptors were inactive. But the U of A researchers found that serotonin receptors are spontaneously active after spinal-cord injury, despite the absence of serotonin. Their study shows that this receptor activity is an essential factor in the recovery of functions like walking. Fouad and Bennett say this significant discovery provides important insight into how the spinal cord responds and changes after an injury, which is essential to developing meaningful treatments.

But, the researchers add, there is a dark side. While the serotonin receptors remain active after injury, they are permanently¹¹ turned on. Fouad and Bennett say this activity is what contributes to muscle spasms¹²（肌肉痉挛） , a common problem for people with severe spinal-cord injury. The pair says the next step in helping¹³ patients who won't be able to regain¹⁴ control of muscle contractions is to examine how to block these serotonin receptors to stop the spasms from occurring, in particular by using already available drugs or by designing more targeted drugs.