[Neurobiological aspects of addictive drugs].

Increasing insight into the molecular and cellular mechanisms of drugs of abuse has been obtained during the last decade. Such drugs exert several of the effects related to their abuse potential by interacting with the mesocorticolimbic dopaminergic system. Single doses of several drugs of abuse increase dopamine activity in nucleus accumbens, which is related to reward and reinforcement. Repeated administration may result in development of tolerance, but also in behavioral sensitization and conditioning. These processes alter subsequent drug-related behaviours and may contribute to relapse to drug taking.