Imaging dopamine transmission parameters in cannabis dependence.

Low striatal dopamine D2/3 receptor (D2/3) availability and low ventrostriatal dopamine release have been observed in alcoholism, cocaine and heroin dependence. Multiple studies to date have examined D2 availability in cannabis dependence and have consistently failed to demonstrate alterations. In addition, the response of the dopamine system to an amphetamine challenge and to a stress challenge has also been examined, and did not show alterations. We review these studies here and conclude that cannabis dependence is an exception among commonly abused drugs in that it is not associated with blunting of the dopamine system.