AsianScientist (Aug. 16, 2012) – A team of Australian and US scientists have shown that addiction to opioids such as morphine and heroin can be blocked in rats.
The results, which could potentially lead to new co-formulated drugs that assist patients with severe pain, as well as helping heroin users to kick the habit, have been published in the Journal of Neuroscience.
“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,” said lead author Dr. Mark Hutchinson of the University of Adelaide.
The researchers showed that the immune response to opioids in rats could be blocked using a drug called (+)-naloxone (plus-naloxone), which provides a selective blockade of this response. They also discovered that addiction to opioids is mediated through a 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. The problem is that TLR4 then acts as an amplifier for addiction,” said Hutchinson.
According to Hutchinson, the drug (+)-naloxone automatically shuts down the addiction to opoids and cuts out behaviors associated with addiction in rats. Neurochemical changes in the brain take place, with dopamine, the chemical important for providing that sense of ‘reward’ from the drug, no longer being produced.
“The drug that we’ve used to block addiction, (+)-naloxone, is a non-opioid mirror image drug that was created by Dr. Kenner Rice in the 1970s,” said senior author Professor Linda Watkins from the Center for Neuroscience at the University of Colorado Boulder.
“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 added.
The researchers are hopeful that clinical trials will take place within the next 18 months.
The article can be found at: Hutchinson MR et al. (2012) Opioid Activation of Toll-Like Receptor 4 Contributes to Drug Reinforcement.
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Source: University of Adelaide; Photo: Joshua Burton/University of Adelaide.
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