The effects of drugs of abuse on clock genes

Daily fluctuations of the behavioral and pharmacological effects of drugs of abuse such as cocaine, morphine or alcohol are observed for several years. Since the discovery of the molecular components of the biological clock, the so-called "clock genes", several studies have further confirmed the inter-relationship between drugs of abuse and biological rhythms. Indeed, drugs of abuse have been shown to clearly induce specific expression changes in clock genes depending on the brain area, the mode of administration or the specific clock gene. On the other hand, increasing evidence for a clear involvement of several clock genes in the development of several drug-induced behaviors has been shown. The present review summarizes these recent findings and reveals the complexity, as well as the specificity, of the interrelation between drugs of abuse and clock genes.