Brain molecules similar to the active compound in marijuana help to regulate alcohol consumption, according to new reports by scientists. In studies conducted with a strain of mice known to have a high preference for alcohol, the scientists found greatly reduced alcohol intake in mice specially bred to lack CB1, the brain receptor for innate marijuana-like substances known as endocannabinoids. The effect was age dependent, the Bethesda group found. The New York scientists showed that the endocannabinoid system activates a brain region known as the nucleus accumbens, which plays a major role in mediating the rewarding effects of alcohol.