The study, revealing differences in dopamine neurons between postmortem brain tissue from cocaine users and controls, appeared in the January issue of the American Journal of Psychiatry. Little and colleagues David Krolewski, M.S., Lian Zhang, Ph.D., and Bader Cassin, M.D., assessed the integrity of the dopamine system in brain tissue from 35 known cocaine users and 35 nonusers matched for age, sex, race, and cause of death. Using tissue from the striatum, an area of the brain with the highest concentration of dopamine neurons, they measured the level of VMAT2, a protein that pumps dopamine molecules into storage vesicles; VMAT2’s binding availability to a selective radiotracer molecule, another assessment of VMAT2 presence and activity; and the overall dopamine level to find how much was available at the time of death. They found that all three levels were lower in cocaine users than in nonusers. And levels tended to be lowest in cocaine users who were diagnosed as having cocaine-induced mood disorders at the time of their deaths.