[Chronobiological analysis of behavior of the intact and pinealectomized rats in the open field test]

It was shown that adaptation to experimental conditions does not result in complete extinction of rat exploratory activity in the open-field test, as it was thought earlier. Behavior of rats is rhythmic. It can be described by a set of infradian oscillations with the periods about 30.4, 18.2, 13.5, 9.3, 7.3, 5.7, and 3.5 days. Pinealectomy does not abolish the infradian rhythmicity of behavioral parameters but modifies it. These findings allow the pineal gland to be considered as an organizer of biorhythms of animal behavior within a wide range of periods including the infradian as well as circadian and seasonal oscillations.