Using morphine after abdominal surgery may prolong pain, researchers find

November 12, 2013

Using morphine to fight the pain associated with abdominal surgery may paradoxically prolong a patient's suffering, doubling or even tripling the amount of time it takes to recover from the surgical pain, according to researchers at the University of Colorado Boulder.

The research team from CU-Boulder's Department of Psychology and Neuroscience—led by Peter Grace, a postdoctoral research fellow, together with Erika Galer, a professional research assistant—was able to identify the mechanism that caused the prolonged pain. The scientists found that both the morphine and the surgery itself excited in the nervous system, causing them to send out additional pain signals to the surrounding nerves.

The research findings, which involved a study using rats, are being presented today at the annual meeting of the Society for Neuroscience in San Diego.

"After —even without using any drugs to treat the pain—the glial cells would be activated and they would contribute to the postoperative pain," Grace said. "What we're saying is, if you give them morphine, we also know that contributes to the pain. If you're putting both of those on top of each other, you're going to have a prolonged period of pain."

Past research at CU-Boulder and elsewhere has shown that, while morphine is an effective painkiller, it can also work against itself. Morphine binds to a receptor on neurons to dull the pain, but scientists now know that morphine also binds to a receptor on glial cells in the brain called TLR4, causing them to become excited and intensify the pain.

In the new study, the researchers found that rats that were given morphine for two weeks prior to surgery to treat pre-existing pain—but that were not given morphine after the procedure—took six weeks to fully recover from postoperative pain compared with two weeks among rats that were not given the painkiller.

In a second experiment, rats that were treated with morphine for a week after the surgery took four weeks to recover from the postoperative pain compared with two weeks among the control group of rats.

"We're seeing the pain prolong for weeks after the discontinuation of morphine," Grace said.

The research team also tested the effects of the drug (+)-naloxone, which inhibits morphine from binding to the glial cells and exciting them. They found that the use of (+)-naloxone along with the morphine eliminated the extended effect.

The researchers are now studying in more detail how morphine excites glial cells and how (+)-naloxone works to block that process. A better understanding of that pathway in the brain may help researchers find a wider variety of drugs that could be administered along with in the future to limit postoperative .

Explore further: Researcher finds method to improve morphine's effect on managing pain

Related Stories

Researcher finds method to improve morphine's effect on managing pain

October 4, 2013
A method to prevent the body from developing tolerance to morphine, a powerful and commonly used pain medication, has been discovered by a Georgia State University researcher.

Multimodal analgesia lessens post-op morphine needs

August 23, 2013
(HealthDay)—A multimodal analgesia combination appears to be safe and effective for pain relief after lumbar decompressive laminectomy, according to a study published in the August issue of the Journal of Spinal Disorders ...

Codeine could increase users' sensitivity to pain

September 12, 2013
Using large and frequent doses of the pain-killer codeine may actually produce heightened sensitivity to pain, without the same level of relief offered by morphine, according to new research from the University of Adelaide.

Tens of thousands lack pain medication in Senegal (Update)

October 24, 2013
Tens of thousands of people in Senegal struggling with advanced cancer and other illnesses are left with only basic headache medicines to treat their pain because the country does not have enough morphine in stock, according ...

Centipede venom could lead to new class of pain drug

September 30, 2013
A protein found in centipede venom could be developed into a drug to treat chronic pain that is as effective as morphine but without the side effects, researchers say.

Recommended for you

Brain stimulation may improve cognitive performance in people with schizophrenia

July 24, 2017
Brain stimulation could be used to treat cognitive deficits frequently associated with schizophrenia, according to a new study from King's College London.

New map may lead to drug development for complex brain disorders, researcher says

July 24, 2017
Just as parents are not the root of all their children's problems, a single gene mutation can't be blamed for complex brain disorders like autism, according to a Keck School of Medicine of USC neuroscientist.

Bird songs provide insight into how developing brain forms memories

July 24, 2017
Researchers at the University of Chicago have demonstrated, for the first time, that a key protein complex in the brain is linked to the ability of young animals to learn behavioral patterns from adults.

Research identifies new brain death pathway in Alzheimer's disease

July 24, 2017
Alzheimer's disease tragically ravages the brains, memories and ultimately, personalities of its victims. Now affecting 5 million Americans, Alzheimer's disease is the sixth leading cause of death in the U.S., and a cure ...

Illuminating neural pathways in the living brain

July 24, 2017
Using light alone, scientists from the Max Planck Institute of Neurobiology in Martinsried are now able to reveal pairs or chains of functionally connected neurons under the microscope. The new optogenetic method, named Optobow, ...

Working around spinal injuries: Rehabilitation, drug treatment lets rats recover some involuntary movement

July 24, 2017
A new study in rats shows that changes in the brain after spinal cord injury are necessary to restore at least some function to lower limbs. The work was published recently in the journal eLife.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.