U of S scientists find possible cure for addiction

Tessa Vanderhart Staff

Chronic drug addiction may be treatable by blocking a signalling passageway in the brain, according to researchers at the University of Saskatchewan.

A recently discovered peptide can block the pleasure associated with drugs — meaning that it can prevent the “highs” that drive substance abuse. Because it interferes with the chemical reaction that occurs in every user’s brain, this protein could be a “universal strategy for the treatment of substance abuse,” according to U of S psychiatry professor Xia Zhang.

Zhang’s research team, based in the Neuropsychiatry Research Unit and Neural Systems and Plasticity Unit at the U of S, will publish its findings in the March issue of Nature Medicine.

“Our peptide,” as Zhang referred to it — technically named PTEN — is actually one part of a very complex brain process: reward.

Neurotransmitters and brain chemicals send messages through the brain by attaching themselves to receptors. For the reward process, this is largely done by dopamine and serotonin.

Zhang said that most addictions are linked to more active and more numerous dopamine receptors, and this peptide can determine how often these receptors get activated by abused substances.

PTEN is a naturally occurring molecule that blocks serotonin receptors, preventing the effect of a drug.

Rats trained to seek nicotine or THC in a white box were given the molecule, or salt as a control.

When rats were treated with this manipulated PTEN, the drug-reward process was effectively thwarted: they showed no special interest in the white box. Further testing showed that no effects of the drugs were realized, including those commonly associated with addiction, craving and withdrawal.

Though the tests examined how PTEN blocks the effects of nicotine and THC (the active ingredient in marijuana), Zhang said that it could be used to cure addictions to other drugs, such as cocaine, heroin and methamphetamine, which use the same reward pathways.

Zhang cautioned, though, that the research is still in its preliminary stages. Though it has been shown to be relatively safe in rats, it will be years before the peptide is tested on humans. Even then, the potential negative effects of the molecule must be considered.

“Because the action of a dopamine neuron is responsible for the presence of naturally occurring [responses to] events such as food or sex,” noted Zhang, “it is possible our peptide could make people unhappy, because it can suppress happiness or pleasure.”