Implications of endogenous opioids and dopamine in alcoholism: human and basic science studies.

We investigated the endogenous opioid system and its role in mediating the reinforcing effects of ethanol that lead to high ethanol consumption as a biochemical marker of an individual's vulnerability to excessive ethanol consumption. We performed studies using human subjects with [high risk (HR)] and without [low risk (LR)] a family history of alcoholism to supplement our studies with experimental animals bred selectively for high- or low-ethanol consumption. HR subjects had lower basal plasma beta-endorphin levels as compared with LR subjects, but they had a more pronounced release of beta-endorphin after exposure to ethanol.