To induce an artificial hypometabolic state (AHMS) in rats and hamsters (non-hibernating and hibernating rodents, respectively), these animals were subjected to the complex action of hypoxia, hypercapnia, darkness, and low temperature. Natural winter hibernation was also induced in hamsters by housing them in a dark cold chamber. During recovering from the artificial and natural hypometabolic states, we recorded EEG activity (leads were implanted in the frontal and parietal cortices), EMG of the neck muscles, and body temperature. The initial period of self-heating after the AHMS in both species and that in hamsters after hibernation was characterized by low amplitudes of EEG and EMG and clearly pronounced depression of EEG oscillations of all frequency ranges, but with relative predominance of δ oscillations (the latter phenomenon may be partly due to superposition of ECG activity on EEG). In the course of further self-heating of animals, the EEG amplitude increased, and its spectral composition changed. The power of some EEG rhythms reached the maximum, and then the EEG composition was normalized successively beginning from the δ range; then the θ and α ranges and, finally, the βrange were normalized. We observed a certain parallelism between changes in the power of b activity in the composition of EEG and increase in the intensity of muscle activity. Patterns of EEG activity corresponding to one functional state or another (active or passive wakefulness, slow-wave sleep, or paradoxical sleep) were normalized in hamsters approximately two times faster than in rats.
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Shylo, A.V. Dynamics of the Electrographic Indices in Rats and Hamsters Recovering from Artificial and Natural Hypometabolic States. Neurophysiology 47, 84–91 (2015). https://doi.org/10.1007/s11062-015-9502-5
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DOI: https://doi.org/10.1007/s11062-015-9502-5