Nora Volkow: Two paths to the future pg. 7
PET scans taken at Brookhaven National Laboratory suggest that the brains of obese individuals have fewer dopamine D2 receptors than do brains of normal controls. A radiolabeled compound (raclopride) that binds to the receptors was used to determine receptor concentration. Red spots in an averaged image of the control brains (top left) indicate a greater concentration of raclopride, and thus more D2 receptors, than are present in an averaged image of the obese group (top right). Overall brain metabolism, measured by the concentration of FDG, a radiotracer for glucose, did not differ significantly between the two groups (bottom panel). Since dopamine modulates motivation and reward circuits, the researchers concluded that dopamine deficiency in obese individuals may perpetuate pathological eating as a means to compensate for decreased activation of these circuits.
Reprinted from The Lancet, Vol. 357, Wang GJ, et. al., "Brain dopamine and obesity," pages 354-357, © 2001, with permission from Elsevier.
During the next few years, the Brookhaven scientists documented reduced levels of dopamine D2 receptors in the brains of alcoholics, heroin abusers and methamphetamine addicts. In addition, they found methamphetamine caused inflammatory changes in the brain that were associated with loss of memory, attention and motor skills.
In 2001, the Brookhaven group, led by Gene-Jack Wang, M.D., reported that obese people—like those addicted to alcohol, cocaine or methamphetamine—have lower-than-normal levels of dopamine D2 receptors.