Diurnal rhythm corticosterone in fasted rats.

The diurnal rhythm of plasma and adrenal corticosterone level was examined in fed male Wistar rats and in these fasted for 24 and 48 h. In fed animals a remarkable diurnal rhythm of both parameters was found showing a nadir at the beginning and a zenith at the end of light period. After 24 h of fasting the zenith was shifted to the beginning of dark period without any other changes. After 48 h of fasting remarkable shifts were found resulting in a nadir at the beginning of dark period and a zenith at the middle of light period.