The scientists demonstrated that in mice, five drugs of abuse (each with different mechanisms of action) and stress enhanced the transmission of electrochemical signals in dopamine neurons, which previous research suggests may be involved in addiction.
In the study, the scientists administered cocaine, amphetamine, morphine, nicotine, ethanol, or the nonaddictive psychoactive medications, fluoxetine and carbamazepine, to groups of mice. The addictive substances caused an increase in the signaling to dopamine neurons while the nonaddictive drugs did not.
Certain drugs of addiction and stress appear to produce similar changes on dopamine signaling, which may play a role in addiction. This also may contribute to the effects of stress on drug seeking and relapse. Understanding the effects of drugs of abuse and stress on brain circuitry may aid in developing therapeutic medications to treat addiction.
This study was published by lead investigator Dr. Robert Malenka in the February 2003 issue of Neuron. It was funded, in part, by the National Institute on Drug Abuse.
