ADVANCED BIO-LUMINESCENCE MICROSCOPY

CLOCKING ON It has been clearly established that a structure in the hypothalamus of the mammalian brain, called the suprachiasmatic nucleus (SCN), contains a ‘daily clock’, which generates near 24 hour (i.e. circadian) rhythmic variations in both physiology and behaviour. This clock is synchronised to changes in environmental illumination (i.e. day/night variations) by light information, which is conveyed directly to the SCN by a specialised input from the eye. The SCN neurons send clock information to the rest of the brain and body via nerve pathways and secretion of particular chemicals. The SCN is composed of different cell types, differentiated in part on the basis of the kinds of neurochemicals that they make as well as their location within the SCN. Further, some SCN cells contain the necessary molecular apparatus to function as single cell timekeepers (‘clock cells’), whereas others lack this property. Key to progressing with research is to be able to identify clock cells and the chemicals via which they communicate to one another as well as the rest of the brain.