Some habits are hard to break. Others become addictions. The latter group could be a figment of the past thanks to a new universal addiction-blocking substance developed by an international research effort led by the University of Saskatchewan.
The team created a peptide, a short chain of amino acids, from PTEN, a natural enzyme that acts on the ventral tegmental area, the reward center of the brain, where most drugs take effect. The peptide blocks the natural rewards that an addict experiences from an increase in serotonin—a neurotransmitter associated with learning, sleep and mood—when taking his or her substance of choice. The regulation of serotonin then modulates the levels of dopamine, a neurotransmitter active in the brain’s pleasure system.
"Our peptide decreases the activity of dopamine neurons located in the brain region responsible for rewards," said Xia Zhang, associate professor of psychiatry at the University of Saskatchewan.
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The study published in the March issue of Nature Medicine found that rats given large doses of both nicotine and THC, the active ingredient in marijuana, for eight days straight would show no signs of addiction or withdrawal when treated with the peptide after their course of the illicit substance ran out.
These findings suggest there could be a universal strategy to treating drug addictions of all kinds. While the rats in this study were addicted to nicotine and THC, Zhang says the peptide could also help fight addictions against cocaine, heroin and even methamphetamines.
However, both Zhang and Rémi Quirion, scientific director of the Canadian Institutes of Health Research's Institute of Neurosciences, Mental Health and Addiction who oversaw the research team, stressed that there is a long way to go before the peptide would be ready for use in humans.
The chemicals that wash over a human brain while under the influence of a drug are more complex than those that are active in a rat brain, and the peptide only blocks out serotonin receptors right now. Also, it’s more difficult to inject the peptide directly into a human brain.
"Probably what will happen is that medicinal chemists will try to reproduce a molecule that will mimic the effect of this peptide," said Quirion.
But, he stressed, even this breakthrough is years away.