Effect of Aging on Circadian Activity in Gray Mouse Lemurs
Source: International Journal of Primatology, Volume 22, Number 1, February 2001 , pp. 25-42(18)
Abstract:Microcebus murinus s a very photoperiod-dependent primate with a potentially extended longevity (13 years). Reduction of artificial seasonal cycles allows acceleration of the aging process. Under these conditions, age is defined according to the number of seasonal cycles. We conducted experiments in order to assess the effects of aging upon (1) the main parameters (period: ; duration: α) of the circadian activity–rest rhythm; and (2) the plasticity of the response to light, which is the main entraining factor of the internal clock. We studied the evolution of and α through two types of experiments: a transverse one comparing 36 males of various ages (1–13 seasonal cycles) and a longitudinal one following 2 pairs of males from the same litter (one from each pair was maintained under natural cycle while the other was submitted to a shortened cycle) over 54 months. Results from transverse experiments demonstrated no statistical difference in and α with age except in 4 senescent (>10 cycles) subjects in which these two parameters were decreased. Longitudinal experiments confirmed this tendency. The plasticity of responses to light, resynchronization after a shift of the day–night cycle, or shift of activity onset after presentation of a light pulse at various circadian times was unaffected by aging. Taken together, the data demonstrate that the parameters of the circadian activity–rest rhythm remain stable over a long span of life and/or that light remains a powerful entraining parameter even in very old individuals.
Document Type: Regular Paper
Publication date: February 1, 2001