Prof.dr. J.H. Meijer

the biological clock: from basic mechanisms to clinical applications

Workshop Leader: Prof.dr. J.H. Meijer,

Department: Neurophysiology, Leiden University Medical Center

Twenty-four hour rhythms can be observed at the level of gene expression, cellular metabolism, endocrine function, physiology and behavior.

In mammals, including humans, the major circadian pacemaker (circa: about; dies: day) driving these rhythms is located in the suprachiasmatic nuclei (Scn) at the base of the hypothalamus. Neurons of the Scn have a genetic basis for the generation of circadian rhythms. Light information reaches the Scn via a specialized neuronal projection, which contains glutamate as its major neurotransmitter. Via this pathway, the endogenous rhythm of the circadian clock becomes synchronized to the environmental light-dark cycle.

The presence of 24-hour rhythms in many of our physiological functions can be used to improve the timing of drug delivery, and to reduce side effects. In the elderly, the circadian system deteriorates, leading to sleeping problems during the night and to reduce alertness during the day.