Function and Pharmacology of Circadian Clocks

Biological timing systems are complex structures in higher organisms, generating biological and physiological functions with a periodicity of approximately 24 h. Knowledge of the structure and function of biological clocks has emerged from research on both invertebrate and vertebrate models. In humans, the master clock is located in the hypothalamus in the brain. Daily rhythms such as the sleep–wake cycle and hormonal rhythms can be modulated and disturbed by a number of pharmacological compounds. Drug therapy can be administered in a circadian fashion (chronopharmacology), thus taking into account the powerful circadian impact on drug toxicity and efficacy. This review will describe circadian systems and pharmacological impact on the timing structures. Keywords: circadian rhythm; pacemaker; clock gene; chronopharmacology; lithium; antidepressants; benzodiazepines; cytokines