Assessment of Circadian and Light-Entrainable Parameters in Mice Using Wheel-Running Activity.

In most organisms, physiological variables are regulated by an internal clock. This endogenous circadian (∼24-hr) clock enables organisms to anticipate daily environmental changes and modify behavioral and physiological functions appropriately. Processes regulated by the circadian clock include sleep-wake and locomotor activity, core body temperature, metabolism, water/food intake, and available hormone levels. At the core of the mammalian circadian system are molecular oscillations within the hypothalamic suprachiasmatic nucleus. These oscillations are modifiable by signals from the environment (so called zeitgebers or time-givers) and, once integrated within the suprachiasmatic nucleus, are conveyed to remote neural circuits where output rhythms are regulated. Disrupting any of a number of neural processes can affect how rhythms are generated and relayed to the periphery and disturbances in circadian/entrainment parameters are associated with numerous human conditions. These non-invasive protocols can be used to determine whether circadian/entrainment parameters are affected in mouse mutants or treatment groups. Curr. Protoc. Mouse Biol. 1:369-381 © 2011 by John Wiley & Sons, Inc.