Circadian rhythm of rectal temperature in young and adult rats under different conditions of food access.

The circadian rhythm of rectal temperature has been evaluated in young (1-month old) and adult (9 month old) female Wistar rats. The animals were housed in metabolic cages in LD 12:12 having food in powder and tap water ad libitum. The single cosinor analysis showed high statistical significance (at least p less than 0.01) in order to circadian rhythm of rectal temperature. The comparisons of the mean cosinor evaluations of circadian rhythm in the 2 differently aged groups do not show significantly different parameters for a 95% of confidence. Two more groups of animals, of the same age, strain, sex and environmental conditions, have been studied. These rats had food admittance in the first 4 h of the dark span (1200.1600) only. In this case too, no significant difference has been evidenced between young and adult rats in any parameters of circadian rhythm for a 95% of confidence. Therefore the 2 pools of animals (young and adult one together because of the already demonstrated lack of difference between the 2 groups) in ad libitum and restricted feeding regimen have been compared. No significant difference has been shown between the 2 groups regarding mesor, while Hotelling's test showed significant differences for amplitude and acrophase. Z9 1