Scientists used to think of alcohol as a membrane disruptor with a generalized effect all over the brain, as the small molecule can freely diffuse across the blood–brain barrier. They now know that there are particular cells in the brain that alcohol targets by binding certain hydrophobic pockets on their surface receptors. The gamma-aminobutyric acid (GABA) receptor is one of these. "Alcohol is an indirect GABA agonist," says Koob.