This text is part of the special Research section
And if drug addiction was not only a disruption of the mechanisms of pleasure? This is somewhat the idea behind the research of Saïd Kourrich, professor in the Department of Biological Sciences at UQAM. The holder of the Research Chair in Neurobiology of Mental Health is trying to elucidate a new mechanism of cocaine addiction.
It all started from a discovery that we made a bit by chance in 2018, which revealed a completely new mechanism of addiction without dopamine [le neurotransmetteur du plaisir immédiat] explains the researcher, who has been interested in the cellular mechanisms of addiction for more than 25 years.
What this discovery suggests is that a drug could create addiction other than by disrupting the mechanism of immediate pleasure. He gives the example of a person with a depressive or anxious tendency whose consumption would be more like a gesture of self-medication. “According to this logic, if she takes the drug not for pleasure, but to reduce pain, this involves other mechanisms. »
The researcher explains that all the knowledge acquired around dopamine over the past 45 years has not yet made it possible to develop a cure for drug addiction. “There are treatments to alleviate symptoms and facilitate withdrawal. But nothing works long term without behavioral treatment. And yet, half of the patients resist and 80% relapse after one year. »
“It’s a question that has obsessed me for a long time,” says Saïd Kourrich, who grew up in an underprivileged suburb of Strasbourg, France, where he witnessed delinquency and drug addiction. “I was passionate about biology and how the body works, and I asked myself very early on, ‘What makes a person enslaved to a substance at the expense of his family, his children or himself? ?” »
The core of the problem
Each drug has a distinct action, but all profoundly alter the electrical circuitry of the brain in several important parts, such as the frontal cortex (responsible for social behavior, decision-making and self-control) or the midbrain (which produces the famous dopamine).
Saïd Kourrich’s laboratory studies a tiny structure in the middle of the brain: the nucleus accumbens. “It determines what we like or dislike and contributes to decision-making by sending a signal to the frontal cortex. »
“Each part of the brain is part of a chain. The nucleus accumbens is the interface between emotion and action. It determines whether you like drugs or not and it’s what tells the frontal cortex: “You’re looking for it”, or not. »
Without questioning what he calls the “dogma” of dopamine, Saïd Kourrich is looking for other mechanisms. He and his team discovered that cocaine affects the nucleus accumbens without involving dopamine. “What we know so far is that cocaine alters the electrical activity of this structure in such a way as to devalue everything you loved at the expense of the drug. »
Integrative approach
After 14 years conducting his research in Minnesota, Maryland and Texas, Saïd Kourrich moved to UQAM in 2018. Thanks to the combined resources of the Research Chair in Neurobiology of Mental Health, but also of the Canadian Institute of Health Research (CIHR) and the American National Institutes of Health, his laboratory (which brings together 7 to 12 researchers depending on the season) implements an integrative approach that uses various techniques and methods.
The first is called “electrophysiology”. It is a question of seeing what happens between the neurons in a situation of dependence. To do this, his team examines neuronal activity in the brains of drug-addicted mice. “We want to know what is happening electrically in this structure. »
When the cells concerned have been identified, the researchers will move on to molecular biochemistry. Using cell cultures, the aim will be to examine how cocaine changes the functioning of the cells in question.
“Once we have understood the mechanisms, we will move on to behavioral experiments. It will be a question of manipulating the cells of living mice to see if we can play on the levers of envy and possibly block addiction. »
Saïd Kourrich admits that every researcher dreams of discovering THE cure, but he will consider himself lucky if he can bring his stone to what will be a collective work.
Nevertheless, he is hopeful that he can elucidate the tipping point where the use of a drug goes from recreational to compulsive, that is to say, to addiction. And who knows? Maybe see what can be readjusted or repaired? “What complicates everything is that for the same drug there can be different processes depending on the individual. »