Simultaneous study of the circadian rhythms of food intake, water intake and renal excretion and analysis of their interrelations in rats.

The circadian rhythms of food intake, water intake and urine and electrolyte excretion were studied simultaneously at 4-hour intervals in male Wistar rats. The animals were housed individually in metabolism cages at constant conditions: temperature 22 +/- 2 degrees C, humidity 60 +/- 10%, light regime at 12 hours light and 12 hours dark. The results were processed using a method for automated analysis of circadian rhythms, which permitted the interpretation of the rhythms both for experimental group and for the population. It was established that the circadian rhythms under consideration had the following time sequence: food intake, water intake, potassium, sodium, chlorides excretion. It was demonstrated that the sinusoidal approximation of the data for food and water intakes was not quite appropriate, since the experimental data showed two maxima during the dark period.