Cocaine use causes profound changes in the brain that lead to an increased risk of relapse due to stress, according to scientists from the University of East Anglia (UEA). Their study (“Orexin-CRF Receptor Heteromers in the Ventral Tegmental Area as Targets for Cocaine”) published in The Journal of Neuroscience identifies a molecular mechanism in the reward center of the brain that influences how recovering cocaine addicts might relapse after stressful events.
The study also identifies a potential mechanism for protecting against such relapses with treatment.
The research team looked at the effects of cocaine in rat brain cells (in vitro) and in live rats, particularly their “cocaine seeking” response to stress. According to lead researcher Peter McCormick, Ph.D., from UEA's School of Pharmacy, “Relapse among cocaine addicts is a major problem. We wanted to find out what causes it. Neuropeptides are messenger molecules that carry information between neurons in the brain. They form the brain's communications system.”
The team looked at the interaction between two particular neuropeptides in the part of the brain that have to do with reward, motivation, and drug addiction among other things.They had speculated that there might be a direct communication between neuroreceptors controlling stress and reward. When tested, this was found to indeed be the case.
“Our research showed that the release of neuropeptides influences activity in this part of the brain and that profound changes occur at the neuroreceptor level due to exposure to cocaine, explained Dr. McCormick. “We showed that cocaine disrupts the interaction between receptors, and these changes could increase the risk of relapse under stressful conditions.”
He added that his group also identified a potential mechanism for protection against such relapse. By restoring the broken interaction, “we may be able to minimize stress-driven relapse in addicts. This research lays the groundwork for the development of such approaches.”
Although the study was carried out with rodents, the same receptors have been shown to impact human stress and drug addiction, noted Dr. McCormick.
“Cocaine has a relatively unique effect on the brain. However, the reward center is crucial for addictive behaviors, he said. “Studies on post-traumatic stress disorder have shown traumatic events can have profound influences on receptors in this region of the brain, perhaps rendering soldiers more prone to addiction. Although speculative, it would not surprise me to see similar results in other situations, whether drug or stress related.”