Scientists Block Brain's Addiction Receptor

Scientists Block Brain's Addiction Receptor

By Valerie Tejeda 08/15/12

The "paradigm shifting" breakthrough has enormous potential to prevent and combat opiate addictions.

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Plus-naloxone may be a key. Photo via

It may soon be possible to block the addictive rewarding effects of opiates in the brain while still allowing painkillers to provide relief, according to a new study, published in the Journal of Neuroscience. Researchers at the University of Colorado and University of Adelaide in Australia discovered an immune receptor responsible for becoming addicted to drugs, and a way to block this receptor—while still allowing pain relief. It's possible that this breakthrough may allow people to use drugs like morphine without the risk of becoming addicted, and help opiate addicts to quit. “It is fundamentally paradigm shifting,” says Linda R. Watkins, a professor in the University of Colorado’s psychology and neuroscience department and a study co-author. “You can’t find a way to solve the problem of addiction if you don’t know there is a key missing player in all the models.” 

Her team identified the receptor 4 (TLR4)—a key immune system component responsible for signaling drug reward—and then blocked this receptor using plus-naloxone, a variant of Narcan. “The most interesting thing about the study is the suggestion that the addition of plus-naloxone may increase the analgesic effect of the opioid while reducing its rewarding effects,” says Wayne Hall, deputy director at the University of Queensland Centre for Clinical Research in Brisbane, Australia. Blocking the crucial receptor was shown to suppress the cravings in heroin-dependent rats, and researchers say plus-naloxone may have a broader application with other addictions as well. “It raises a lot of interesting questions about where plus-naloxone works and how it’s doing that, because we really don’t know that,” says Mark Connor, professor of pharmacology at Macquarie University in Sydney, who wasn't part of the research. “It’s going to provoke a lot of debate in the opioid field. There are going to be people rushing to repeat these experiments.”