A recent study conducted by researchers from the National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism, parts of the National Institutes of Health, has shed light on the brain regions responsible for the addictive potential of drugs. The study, published in Nature Communications, found that a group of brain regions known as the “salience network” is activated after a drug is taken intravenously, but not when the same drug is taken orally.
The findings suggest that drugs that enter the brain quickly, such as through injection or smoking, are more addictive than drugs that enter the brain more slowly, such as when they are taken orally. The study employed PET/fMRI imaging to compare dopamine levels and brain activity in response to methylphenidate administration in twenty adults. Results showed that the rapid release of dopamine with intravenous drug administration corresponds with increased addiction potential, while slower increases with oral intake have a lower addiction risk.
According to Nora Volkow, MD, NIDA Director and senior author on the study, “We’ve known for a long time that the faster a drug enters the brain, the more addictive it is – but we haven’t known exactly why. Now, using one of the newest and most sophisticated imaging technologies, we have some insight.” Understanding the brain mechanisms that underlie addiction is crucial for informing prevention interventions, developing new therapies for substance use disorders, and addressing the overdose crisis.
The study used simultaneous PET/fMRI imaging to observe the differences in dopamine levels and brain activity after participants received a small dose of methylphenidate orally or intravenously. The findings showed that brain regions associated with the salience network were activated only after receiving the injection of methylphenidate, the more addictive route of drug administration, while those same regions were not activated after taking methylphenidate orally, the route with lower addiction potential.
The results provide evidence for a link between specific brain regions and the speed of dopamine increases in response to drug administration. Researchers hope that these findings could lead to the development of new treatments for substance use disorders by targeting the salience network in the brain.