Previous investigations indicate that the aging Fischer 344 (F344) rat undergoes a transition from aging to senescence which is characterized by a rapid decline in body weight and the development of severe cold-induced hypothermia. These observations suggest that the transition from gradual aging to senescence involves general alterations in hypothalamic function. To further investigate this possibility, circadian rhythm of body temperature (CRT) was measured in male F344 rats beginning at age 23 mo. and followed continuously until death via a temperature-sensing radio wave transmitter implanted in the abdominal cavity. The rats were maintained in a room with constant dim light (10-15 lux) at a thermoneutral temperature (24-25°C). Temperature was recorded every 10 mins. Body weights were measured bi-weekly. The age at which body weight displayed a rapid decline ranged from 24 to 32 mo. In general, rats died within 3 weeks of the onset of rapid weight loss. Measures of CRT, daily mean body temperature, rhythm period and amplitude did not differ significantly within each rat during aie period that body weight was stable. However, at the onset of rapid weight loss, daily mean temperature and rhythm amplitude decreased; changes in the period response were inconsistent These data suggest that the altered CRT of aging rats is associated more closely with the transition to senescence (as indicated by the rapid decline in body weight near the end of life) than with chronological age per je. Together with our previous findings, the current observations are consistent with the hypothesis that the transition from gradual aging to senescence reflects altered hypothalamic regulation. (Supported by NIH Grant AG06665 and NASA Grant NAG2-944).
|Original language||English (US)|
|State||Published - 1996|
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Biochemistry, Genetics and Molecular Biology(all)
- Cell Biology