It is generally accepted that the rewarding effects of drugs are due to their ability to increase dopamine (DA) particularly in the nucleus accumbens (NAc) (3). The potency of drugs as well as the mechanism by which they increase DA differs for the various drug classes (4). Interestingly, DA’s role in drug reward (as well as reward in general) does not seem to equate with hedonic pleasure (mediated in part by endogenous opioids and cannabinoids), but instead DA appears to encode prediction of reward, imprinting incentive value to reinforcers (energizing approach behavior) and facilitating learning of reward associations (conditioning) through its modulation of subcortical (including the NAc) and cortical brain regions (reviewed in Reference 5).
