Morphine and heroin addiction can be blocked in the brain by targeting the body's immune system that amplifies drug addiction, a new study found.

The research team from University of Adelaide and University of Colorado is hopeful that the new research will result in the creation of drugs that work along with morphine to ease chronic pain without making the person an addict. The drug can also help reduce addiction in people who use opioids.

Morphine is used to relieve moderate to severe pain in patients who need a constant pain reliever for more than a few days. Morphine belongs to a class of medications called opiate analgesics and works by changing the way the body feels pain. Long term daily use of opioids can lead to physical dependence.     

Morphine is generally prescribed to treat pain in people who are at advanced stages of cancer but now morphine is being prescribed for pains not related to cancer.

Researchers have found that the drug (+)naloxone blocks the immune-addiction response without changing the brain's wiring.

"Our studies have shown conclusively that we can block addiction via the immune system of the brain, without targeting the brain's wiring," said the lead author of the study, Dr. Mark Hutchinson, ARC Research Fellow in the University of Adelaide's School of Medical Sciences.

Researchers say that blocking the immune response will lead to blocking the addiction and that other systems aren't disturbed in this process. According to the scientists, targeting a key structure called TDR4 can help in dealing with drug addiction.

"Opioid drugs such as morphine and heroin bind to TLR4 in a similar way to the normal immune response to bacteria. The problem is that TLR4 then acts as an amplifier for addiction," Dr. Hutchinson says.

The drug works by changing the mechanism of developing an addiction in the brain and removes the "highs" from the drugs, making it easier for the person to kick the habit. The drug changes the neurochemistry of the brain by shutting down the pathway that produces dopamine when it encounters the opioids.

"This work fundamentally changes what we understand about opioids, reward and addiction. We've suspected for some years that TLR4 may be the key to blocking opioid addiction, but now we have the proof,"  said Professor Linda Watkins, from the Center for Neuroscience at the University of Colorado Boulder and the senior author of the study.

Researchers say that the discovery will lead to creation of drugs that will help people on morphine for pain relief without making the person addicted to the drug.  

Dr. Kenner Rice created the drug (+)-naloxone, which is a non-opioid mirror image drug, in the 1970s, Watkins said.

The study is to be published in the Journal of Neuroscience.