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Night and day differences in the food-intake of laboratory rats Wistar and Koletsky strains.

BACKGROUND
Rats have an extraordinary expressive circadian organization and prefer the dark as the optimal condition of its life environment. During darkness, the rhythm of its several parameters reaches the acrophase.


MAIN PURPOSE
The aim was to establish the differences in the level of food-intake of laboratory rats of the Wistar strain and in those of the spontaneously obese rats of the Koletsky strain by means of ad libitum feeding under natural light-dark conditions.


METHODS
The levels of day and night food consumptions in both strains of rats, Wistar and the spontaneously obese Koletsky strain, were studied within the period from January 10th to 20th, (males), and from April 16 to 26, 1990, (females). The animals were fed by Larsen's diet under natural light conditions. The data were evaluated by means of the t-test.


RESULTS
It was detected that during the period between 5 o'clock PM and 6 o'clock AM the male rats of the Wistar strain consumed 80% and the female rats 79% of their total daily amount of food. Food consumption of the Koletsky rats during the period from 5 o'clock PM to 6 o'clock AM in males reached the value of 72% and in females 74%.


CONCLUSIONS
There were detected significant differences in circadian food-intake in both strains. Besides the nocturnal preference in food-intake of Wistar rats, which is in accordance with the data gained from literature, a similar food-intake with expressive diurnal-nocturnal differences exists also in the spontaneously obese Koletsky rats. Daily food consumption in these male rats was significantly higher when compared to the Wistar strain. (Tab. 1, Fig. 1, Ref. 5.).