Gene expression induced by drugs of abuse.

The transition from infrequent drug use to addiction (i.e. the loss of control over consumption of a drug) probably involves changes in gene expression that restructure neural circuits in the brain. The number of genes that have been demonstrated to change expression in response to drugs has increased rapidly in recent years owing to microarray technology, which allows measurement of thousands of genes at one time. It is now important to identify which of these changes are causally related to the compulsive behavior associated with drug addiction, and which are non-specific changes related to general features of arousal or other physiological responses (e.g. stress, altered body temperature or energy metabolism).