An international team of scientists say they can block addiction to heroin and morphine, while at the same time decreasing pain.
The researchers, from the University of Adelaide and University of Colorado in Boulder, say they have discovered a key mechanism in the body’s immune system that amplifies addiction to these drugs. Laboratory studies have then shown that the drug (+)-naloxone (pronounced: PLUS nal-OX-own) will selectively block addiction.
“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, Mark Hutchinson, Ph.D., of the University of Adelaide’s School of Medical Sciences.
“Both the central nervous system and the immune system play important roles in creating addiction, but our studies have shown we only need to block the immune response in the brain to prevent cravings for opioid drugs.”
The team focused its research efforts on the immune receptor known as Toll-Like receptor 4 (TLR4). “Opioid drugs such as morphine and heroin bind to TLR4 in a similar way to the normal immune response to bacteria,” he explained.
“The problem is that TLR4 then acts as an amplifier for addiction.”
“The drug (+)-naloxone automatically shuts down the addiction,” he continued. “It shuts down the need to take opioids, it cuts out behaviors associated with addiction, and the neurochemistry in the brain changes. Dopamine, which is the chemical important for providing that sense of ‘reward’ from the drug, is no longer produced.”
The new research “fundamentally changes what we understand about opioids, reward and addiction,” added Dr. Linda Watkins, a professor in the Center for Neuroscience at UC Boulder. “We’ve suspected for some years that TLR4 may be the key to blocking opioid addiction, but now we have the proof.”
The drug used to block addiction, (+)-naloxone, is a non-opioid mirror image drug that was created by biochemist Dr. Kenner Rice in the 1970s, she explained.
“We believe this will prove extremely useful as a co-formulated drug with morphine, so that patients who require relief for severe pain will not become addicted but still receive pain relief,” she said.
The researchers say clinical trials may be possible within the next 18 months.
The study, funded by the National Institute on Drug Abuse (NIDA) in the United States and the Australian Research Council (ARC), was published in the Journal of Neuroscience.
Source: The University of Adelaide