Cocaine study raises questions about all addictions

Tuesday, 3 February 2015

International research involving the University of Adelaide has pointed to a potential new treatment for cocaine addiction, and could have implications for all types of drug addictions, according to the researchers.

A team led by the University of Adelaide and University of Colorado has discovered a mechanism in the body's immune system that amplifies addiction to cocaine.

The results of their research, published today in the Nature journal Molecular Psychiatry, also shows that cocaine’s rewarding properties can be blocked, thanks to a drug that prevents the immune system's response.

The team has focused its research efforts on the role of the immune receptor known as Toll-Like receptor 4 (TLR4).

"Our previous studies have shown that TLR4 is responsible for amplifying addiction to opioid drugs such as heroin, but this is the first time we've discovered it has a key role to play in cocaine addiction," says Professor Mark Hutchinson, ARC Research Fellow in the University of Adelaide's School of Medical Sciences.

Lead author Alexis Northcutt, from the Center for Neuroscience at the University of Colorado Boulder, says: "We've demonstrated conclusively that cocaine interacts with TLR4 to produce a pro-inflammatory effect in the brain. The effect is necessary to convey the drug's rewarding effects. Without it, reward is greatly reduced.

"Combined with our previous work, this suggests that the immune signalling may be a key mechanism underlying the rewarding and reinforcing effects of drugs such as opioids, cocaine, and potentially other abused substances, like methamphetamine and alcohol," she says.

In laboratory studies, the researchers had previously demonstrated that opioid addiction could be blocked, by using the drug (+)-naloxone (pronounced: PLUS nal-OX-own) to prevent opioids from binding to TLR4.

"The cocaine study has had the same result, which is unique in itself. We now have two major drugs of addiction that are both being amplified by TLR4, which we can stop through the use of (+)-naloxone," says Professor Hutchinson, who is also Director of the ARC Centre of Excellence for Nanoscale BioPhotonics at the University.

"These are very exciting and encouraging results. It means that we could potentially see a single intervention for a wide range of addictions in the future."

This research is supported by the National Institute on Drug Abuse, the National Institute on Alcohol Abuse and Alcoholism and the Department of Defense in the United States, and the Australian Research Council.

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