Research finds morphine may be wrong drug for treating spinal cord injuries
A researcher in the Texas A&M University Department of Psychology is pioneering a study that could change the future of spinal cord injury treatment.
Michelle Hook, an associate research professor in the College of Liberal Arts, has found that the morphine used to alleviate pain in those with spinal cord injuries may ultimately cause more harm than good. She is collaborating with Sandra Garraway and James Grau, both researchers in psychology at Texas A&M, to conduct the study.
As an opiate analgesic, morphine is one of the most frequently prescribed medications for treatment of chronic pain after a spinal cord injury. Hook’s research, which is funded by a grant from the National Institute on Drug Abuse, assesses the effects of morphine on rats with spinal cord contusions.
For the preliminary stage of the study, the researchers assessed the rats’ recovery after a single dose of morphine was injected directly onto their spinal cord (on the day following the injury). They found that the rats showed a decreased ability to recover – their locomotor abilities were compromised, they had difficulty gaining weight, and they were more likely to develop behavioral signs of neuropathic pain. Hook’s data suggest that doctors should use caution when administering morphine in the acute phase of spinal cord injury.
The next phase of Hook’s research involved a model that emulates actual patient treatment. The rats were given a lever with which they could self-administer morphine at varying doses. Hook’s lab is the first to use the self-administration paradigm in rats with spinal cord contusion.
“We found that these rats self-administer very large doses of morphine,” said Hook. “These doses far exceed that needed for pain relief.”
Interestingly, the amount of morphine administered by the rats with a spinal injury depended on the dose they received with each lever press and the phase of injury in which the drug was given. In the initial few days following injury, the rats administered less morphine than non-injured rats and they continued to administer less if a moderate dose of morphine was given with each lever press.
According to Hook and her team, the results of this study provide evidence that injury may reduce the addictive potential of morphine in the early phase, but it does not negate it. The injured rats displayed signs of addiction when a high dose of morphine was administered with each lever press. The researchers aim to understand what changes in the spinal cord reduce the potential for addiction and the effects of the self-administered morphine on recovery of function.
“Already, people are thinking a little bit more carefully about whether they use morphine in the clinic,” said Hook.
Additionally, Hook is trying to determine the molecular mechanisms that underlie the effects of morphine. The drug binds to four receptors at a molecular level, and she hopes to determine which receptor morphine binds with to produce the best pain relief and which ones cause adverse effects. This information could lead to better pain management treatments in the future.