Fluctuation of blood glucose level in newborn rats depending on the season and spontaneous motor activity pattern

Abstract

Previously, we demonstrated that in newborn rat pups the blood glucose level changes depending on the spontaneous periodic motor activity (SPMA) pattern. During rest periods, both under dominant decasecond and minute rhythms, the blood glucose level is higher than during activity periods. We also showed that the blood glucose level rises with age reaching the “adult” level by day 10. In the present study conducted on 3–10-day-old rat pups under free behavior conditions, the blood glucose level has been examined at different periods of the activity–rest cycle and at different seasons. It has been established that in newborn rats at all ages tested (3, 5, 7 and 10 days) the lowest glucose concentration occurs in winter. In spring, the glucose level increases reaching its maximum in summer when it is significantly different from those in winter and spring in all age groups except for day 5. In autumn, the glucose level decreases approaching its spring values but still differing significantly from the winter values. In 5-day-old rats, no significant changes in the glucose level at different seasons have been found. These data indicate seasonal fluctuations of the blood glucose level in newborn rats. Meanwhile, during all seasons except for spring the blood glucose level depends on the SPMA pattern. In spring, these differences are smoothed.