Keeping an animal functioning after a cervical spinal cord injury is nearly impossible. An American researcher developed the lower spinal cord rat model in the early 1900s. He found that lesioning the spinal cord of dogs between the eighth and tenth thoracic vertebrae produced hind-limb paralysis while letting animals stay self-sufficient. Yang Teng, director of spinal cord injury research at the West Roxbury Veterans Administration Medical Center (WRVA), first observed very transient breathing disorders while working on a rat version of the model in graduate school. One of his professors had shown that morphine’s respiration-suppressing effects could be counteracted by the serotonin agonist 8-OH DPAT. Teng tried that drug and buspirone on the lower thoracic-injured rats. “It restored their breathing,” he said. “But we knew that the underlying cause of loss of respiratory function in lower- thoracic injury is very different from cervical injury – different neuromuscular systems are involved.”
Teng and Howard Choi, Harvard Medical School clinical fellow in physical medicine and rehabilitation, hypothesized that administering a contusion to half of the spinal cord would keep a cervically injured rat alive. Delivering such a lesion turned out to be difficult. The spinal cord is buried deep inside the body at the neck and thorax.
Choi began his experiments. In the earlier study, Teng delivered serotonin agonist one day after injury and restored breathing in the lower thoracic-injured rats for four hours. Choi delivered the drug four days after injury. Breathing was restored for the same length of time.