Dopamine Triggers Drug-Abuse Memories

Experiments with mice are providing new details about how dopamine signaling in the brain sparks memories that reinforce the allure of addictive drugs (Neuron 2009, 63, 673). John A. Dani and Jianrong Tang of Baylor College of Medicine injected mice with nicotine, the addictive component of tobacco. The researchers showed that multiple doses of nicotine increase long-term potentiation at synapses in the hippocampus, a process that underlies memory formation and learning. They further showed that this process depends on dopamine signaling in the dentate gyrus region of the hippocampus. Dani and Tang then assessed mice that had learned to prefer the cage compartment in which they were dosed with nicotine over another available compartment. The researchers found that development of this learned preference also requires dopamine signaling and can be prevented in mice by administering SCH23390, a benzazepine compound commonly used in lab studies to block the dopamine receptor. The results support the idea that dopaminergic signaling enhances the power of environmental cues—such as a location associated with previous drug use—to stimulate continued drug abuse or relapse in people, Dani notes.