Researchers have discovered a chemical system in the brain that reacts differently in cocaine addicts’ brains, which could help develop new treatment methods. Researchers from UT Southwestern Medical Center found that the amount of blood flow in the “reward” centers of the brain that are associated with drug cravings was different in those who are addicted to cocaine, when compared with non-addicted people. Dr. Bryon Adinoff, lead author of the study and professor of psychiatry at UT Southwestern, said these findings provide a new target for addiction pharmacology.

The study, which was published in the journal Neuropsychopharmacology, studied changes in the cholinergic system in the brain, which involves the neurotransmitter acetylcholine. Disruption of this system has been implicated in Alzheimer’s disease. In animals, acetylcholine has been found to affect how hard an animal will work to obtain drugs. Until this study, the relation of the system to human addiction had not been studied.

The researchers examined the ways in which alterations to the cholinergic system affected the limbic region in the brains of cocaine addicts, which controls emotions, behavior, long-term memory, and learning. They injected two substances—scopolamine and physostigmine, both of which act on acetylcholine receptors—into 23 cocaine addicts who had abstained from the drug for one to six week and 22 non-addicts on two different days. On the third day, the participants were injected with saline. After each injection, participants were given brain scans to examine the blood flow in the limbic region.

Both substances were found to change blood flow in the limbic regions, but the patterns were different between addicts and non-addicts. Dr. Adinoff said that the hippocampus and amygdala were affected, and both of these regions control environmental cues that may encourage someone to keep using cocaine. This suggests that treating addicts with medication that would affect these systems could help reduce drug cravings.

The next step in the study would be to use functional magnetic resonance imaging (fMRI) to examine how the cholinergic system affects decision-making processes, as these can increase the risk of relapse in addicts.

Source: Science Daily, Chemical System in Brain Behaves Differently in Cocaine Addicts, Scientists Find, August 10, 2010