Drug addiction is a neuropsychiatric disorder that leads to one in five deaths in Canada.

While most people who use drugs do so recreationally, in a controlled and non-pathological way, a minority will become addicted. Researchers understand how drugs affect the brain but have yet to determine why only some people develop substance dependence.

Anne-Noël Samaha, professor in the Department of Pharmacology and Physiology at Université de Montréal, is working to elucidate drug addiction. More specifically, she is focused on the neurobiology of stimulant addiction to drugs like cocaine, nicotine and amphetamines.

As part of her research, she turns to animal models to better recognize the conditions under which drug use evolves into addiction, since lab rats can experience reactions that are consistent with those observed in humans.

In addition to studying the rats’ behaviours after they are given drugs, she uses an optogenetic technique to control the activity of their neurons with laser light and a light-sensitive protein while the animals are looking for drugs in their environment. Her goal is to demonstrate the links between neural circuits and drug use patterns.

Professor Samaha and her team have identified an area of the brain that may be involved. Indeed, the amygdala, which is usually associated with anxiety and fear, also plays a part in the reward system. When the researchers increase the neural activity in this region while a rat is seeking drugs, the animal will step up its efforts to find the reward.

Could this mean that a change in the amygdala may contribute to pathological reward-seeking behaviours stemming from a drug or gambling addiction? Further studies are needed, but in the meantime, the observations shed light on the neural circuits that may lead to potential avenues to treat drug addiction in humans.