Grant: Project Grant

Drug addiction is amongst the leading preventable causes of death and illness in the world. In Canada, cocaine is now the most used illicit drug. Drug addiction is involved in the death of one in five people, and addiction costs Canadians nearly $40 billion per year. Over half of people addicted to cocaine seek treatment, but the prevalence of cocaine addiction has not decreased over time. This is in part because there are no approved medications to treat cocaine addiction. To develop new medications, we need to understand how initial cocaine use changes the brain, psychological function and behaviour to promote the transition from casual drug use to addiction. Animal models are on the front lines to achieve this, because laboratory animals can show the characteristic behavioural features of addiction. This in turn allows researchers to study how drugs change the brain to produce these features. Currently, the most widely used procedure to study cocaine addiction in laboratory animals involves allowing them to self-administer cocaine continuously for several hours a day. However, an alternative model has recently been developed, that might better capture the intermittent-rather than continuous-pattern of cocaine use in humans. This new model also appears especially effective in producing addiction-like features in animals. Our goal here is to directly compare and contrast these two models of addiction. We will also focus on cocaine-induced changes in i) the actions of the chemical messenger dopamine, which mediates motivation for rewards, and ii) neuronal activity in brain circuits involving a brain region called the prefrontal cortex, which mediates judgement and self-regulation. We expect that our findings will be critical in helping researchers make informed decisions about how to model addiction-like features in laboratory animals. This in turn will be important in determining directions for new anti-addiction medications in people.