A specific molecule in the brain that is a possible target for treatment to prevent relapses for people who have used cocaine and risk addiction, even after prolonged drug-free periods was described in research last fall at Sweden's Linköping University.

Researchers demonstrated that a receptor for the signal substance glutamate (mGluR5), in a part of the brain called the striatum, plays a major role in relapses. Using mice that were taught to ingest cocaine, the study, led by David Engblom, associate professor of neurobiology at Linköping University, examined events in individuals who lack the glutamate receptor.

The research team explained in an article in the Journal of Neuroscience that drugs become addictive because they "hijack" the brain's reward system, which is actually intended to make it pleasurable to do things that are necessary for survival, such as eating and having sex. This "hijacking" lasts a considerable time and, even though ceased temporarily, can frequently relapse into abuse, especially when the individual is exposed to surroundings that are associated with the drug.

"Our findings show that the mice who lacked the receptor were less prone to relapse. This is due the fact that their reaction to reward had not been etched into their memories in the same ways as in normal mice. The receptor seems to be a prerequisite for objects or environments that were previously associated with taking drugs, or something else rewarding, to create a craving," concluded Engblom.

He hopes that these findings and other studies of mechanisms underlying drug addiction can lead to forms of treatment that is based on malfunctions in the brain of an addict.

Source: Swedish Research Council: www.vr.se1; University of Linköping: www.liu.se