Unusual Pattern of Cerebral Electrical Activity in the Mongolian Hamster (Allocricetulus curtatus) During Heterothermia.

Electroencephalogram (EEG), brain and abdominal temperature, and motor activity were recorded for the first time in 18 adult males of facultative hibernator, the Mongolian hamster, during hibernation under controlled laboratory conditions in winter. At room temperature, clear synchronous circadian rhythms of motor activity and body temperature were observed. In most animals, a gradual decrease in external temperature (from 24 to 4°C) led to a significant increase in motor activity, combined with an increase in the amplitude of circadian oscillations of body temperature. Six hamsters demonstrated torpor bouts and hibernation with radical changes in the EEG up to reaching the isoelectric line, as well as the disappearance of oscillations of brain temperature. It has been found that Mongolian hamsters can easily enter and exit both a state of torpor and a fairly deep hibernation with a decrease in body temperature down to 10°C during normal sleep periods.