Abstract
We examined voluntary wheel activity, body weight, food intake and water drink throughout the life of 36 female virgin Wistar rats fed ad libitum. We also determined the duration from menarche to menopause. The animals were housed in a steel cage with a wheel for voluntary exercise. Twelve rats were ovariectomized at 60 days of age. The mean life span of the intact rats was 755 +/- 191 days. The mean age at menarche and menopause was 45 +/- 13 and 403+/- 56 days, respectively. Both parameters were changed in a particular manner with aging, which was characterized by a numerical formula. Voluntary wheel activity throughout the life span was characterized by increasing and decreasing phases with a peak at 90 days of age. Body weight reached a maximum value (400 g) at 450 days and was characterized by an initial steep increase before menarche, a stagnated phase during estrogen secretion, and a slight temporal increase after menopause. Food and water intake reached a minimum at 450 days. Power spectral analysis confirmed that the menstrual cycle lasted for 4.39 +/- 0.53 days from menarche to menopause. The coefficient of variation of voluntary wheel activity revealed prominent increases in individual differences after menopause. A longer duration between menarche and menopause was significantly related to an elongated life span. [Jpn J Physiol 54 Suppl:S205 (2004)]
