In humans, several drugs [stimulants (12, 13), nicotine (14), alcohol (15, 16) and marijuana (17)] increase DA in the dorsal and ventral striatum. These studies are based on the measurement of DA D2 receptors that are not occupied by DA (receptor availability) and thus able to bind the PET radiotracers (i.e., [11C]raclopride, [18F]fallypride, or [11C]PHNO). By comparing D2/3 receptor availability after placebo and after acute drug exposures, these studies estimate the relative changes in DA (18). Most drugs tested in humans have shown a significant increase in DA in the ventral striatum (where the NAc is located) that was associated with the subjective perception of the drugs as rewarding (reviewed in Reference 19).
