Cocaine May 'Teach' Addiction to Brain—Fast

Just one dose of cocaine may physically change the brain as the body begins "learning addiction," scientists say. They investigated the effect of the drug on mice, and noted that within two hours of being injected with the drug, brain changes were visible, the BBC reports. After two hours, scans showed that mice on the drug developed more dendritic spines—key to forming memories—than did mice injected with water. "Our images provide clear evidence that cocaine induces rapid gains in new spines, and the more spines the mice gain, the more they show they learned about the drug," says a researcher.

At the beginning of the experiment, the mice were placed in a "conditioning box" comprised of two very different rooms linked by a door. After their room preference became clear, they were injected in the opposite room. Afterward, mice tended to hang out on the side where they'd been injected, suggesting "they were looking for more cocaine," says the researcher, per the UC Berkeley News Center. As for us humans, the brain changes could show how "drug-related cues come to dominate decision-making ... leaving more mundane tasks and cues with relatively less power to activate the brain’s decision-making centers." (Click for another fascinating study involving cocaine.)