Body temperature and locomotor activity as marker rhythms of aging of the circadian system in rodents

Most biological functions present rhythmic variations. These rhythms are di stinguished by their period and concern all the levels of biological life. Circadian rhythms follow a periodicity close to 24-h, they allow individual s to survive via adaptation to the periodic variations of environment. Thro ughout the aging process, modifications in circadian rhythms of endocrinolo gical, metabolical and behavioural fields have been found in many animal sp ecies. This review updates the body of knowledge on aging-related alteratio ns of the circadian rhythms of body temperature and locomotor activity: mod ifications in circadian profiles, modifications in the period of free-runni ng rhythms, internal desynchronisations and modifications in entrainment ab ility of these rhythms. (C) 1999 Elsevier Science Inc. All rights reserved.