Long-term cocaine use increases impulsivity in rats

Researchers have widely accepted that impulsivity increases the risk of drug addiction, but the evidence to support this belief is mixed. Exploring the relationship between impulsivity and cocaine use in rats, Yihong Yang and colleagues from the National Institute on Drug Abuse found evidence that contradicts the prevailing view that high impulsivity predicts cocaine use. 

One classification of impulsivity is impulsive choice, which can be studied with risky choice tasks and delay-discounting tasks (DDT). During DDT, impulsive individuals prefer smaller, immediate rewards over larger, delayed ones. In this eNeuro study, the researchers used DDT to categorize how impulsive rats were compared to their peers. After being classified by impulsivity level, the rats went through a cocaine self-administration paradigm; researchers can measure addiction-like behavior by continued cocaine use despite the known presence of unpleasant consequences-foot shocks, in this case. In addition to finding that impulsivity levels did not influence cocaine use, the researchers were surprised to discover that long-term cocaine use increased impulsivity in rats previously considered less impulsive than their peers.

Brain imaging and other assessments revealed that rats with cocaine-driven impulsivity had fewer dopamine receptors and weaker communication between brain regions in a reward-related network. According to the authors, these findings advance our understanding of complex drug–brain circuit interactions and how they influence behavior.