Circadian Rhythm

Changes in sleep patterns can be detected by examining activity continuously over a period of days and nights. We use an infrared beam system that monitors the horizontal locomotor activity of an individual mouse in its home cage environment for 3 days and nights. This allows us to obtain an accurate indication of their sleep-wake cycle as well as overall locomotor activity rates. Changes in the normal circadian rhythm or an increase or decrease in the periods of activity during the normal sleep cycle can indicate genes controlling sleep and can be supportive of therapeutic potential for other conditions, such as depression or schizophrenia, in which normal sleep patterns are disrupted. Only female mice are tested in this assay.

Female mice are individually housed at 4 pm on the first day of testing in 48.2 cm x 26.5 cm home cages and administered food and water ad libitum. Animals are exposed to a 12-hour light/dark cycle with lights turning on at 7 am and turning off at 7 pm. The system software records the number of beam interruptions caused by the animal's movements, with beam breaks automatically divided into ambulations. Activity is recorded in 60, one-hour intervals during the 3 day testing period. Data generated are displayed by median activity levels recorded for each hour (circadian rhythm) and median total activity during each light/dark cycle (locomotor activity) over the 3 day testing period.

Displayed below is a sample graph of how circadian rhythm observations are presented. In comprehensive phenotypic data packages graphs are interactive. Raw or calculated data and statistics can be seen by clicking on points in the graph.

Figure illustrates median ambulatory counts of female mutant mice. Ambulatory counts for wild type littermates (green circle), homozygous (red diamond,) and recent historical wild types (purple line) are plotted against long-term historical ambulatory counts (+/- 2 standard deviations) for wild type animals (green shading). Recent wild type values are calculated from data collected within 60 days of current measures and long-term historical values are derived from data collected on more than 10,000 wild type mice.