A former U of T researcher has discovered an “addiction switch” in the mammalian brain, suggesting that the effects of addiction are reversible.
Published this month in Nature Neuroscience, the study looked at how the rat brain processes the pleasurable, “reward” effects of heroine.
Dr. Steven Laviolette, lead author of the study and currently a post-doctoral fellow in the Department of Neuroscience at the University of Pittsburgh, says he and his colleagues found the addiction switch in the ventral tegmental area (VTA), a structure embedded deep inside the brain involved in processing reward information for all addictive substances, including tobacco.
Our brain cells communicate by means of tiny structures called receptors that send and receive signals. In the VTA, the receptor GABAA controls how reward information is processed, which changes depending on whether or not the drug taker is addicted. When a rat is still in the beginning stages of drug taking, the rewarding sensations are processed in a separate system from the one that gets turned on once the rat has become an “addict.” Why does this happen? When the rat brain is addicted, the balance of a certain enzyme called carbonic anhydrase changes at the site of the GABAA receptor, altering its signals, causing the brain to change its reward-processing system.
Laviolette manipulated the level of carbonic anhydrase so that over just a matter of hours, the brain of the rats that were addicted to heroin, went back to processing reward information in the non-addicted state. The withdrawal period was significantly shortened from the usual duration of several weeks. This study suggests that addiction is not necessarily permanent.
One of the most difficult challenges for addicts to overcome is hauling themselves through the withdrawal period and struggling to avoid relapse. This can be controlled, says Laviolette, once we figure out how to pharmacologically manipulate the addiction switch in the human brain. “If we throw the switch back to the non-addicted state, then the person is no longer going to be craving the drug.”
These findings do not offer hope for addicts in the near future, however. Although the human brain and the rat brain are similar, researchers still need to clarify everything with further studies. They also need to study other addictive substances such as nicotine and alcohol. As Laviolette points out, the move from basic animal research to human application often takes 10 to 15 years, if not longer.
