Accepted in revised form 12 October 2001; recieved 2 August 2001
The effect of 48, 72 and 92 hr water tank deprivation of paradoxical sleep (PSD) on the structure of the sleep-wakefulness cycle (SWC) was studied in cats with chronically implanted electrodes both in the deprivation and postdeprivation period.
Multiparametric analysis (observation on the dynamics of electroneocorticogram, electrohippocampogram, tonic activity of the skeletal muscles, electrocardiogram, eye movement, ponto-geniculo-occipital spikes, etc.) shows a strong stressful impact of the water tank situation on the experimental animal, on the face of which the development of the sleep cycle is being delayed. However, after the lapse of a definite time, in spite of the presence of a high emotional tension and inconvenient situation for taking an optimal position of the body to realize the cycle of sleep, the EEG parameters of the slow wave phase of sleep (SWS) (even at their most profound expression) develop rather intensively and last long enough to trigger the paradoxical phase of sleep (PS). As to the PSD in this situation, it is accomplished as behavioral awakening of the animal induced by the fear reaction associated with the development of the skeletal muscle atonia. Since similar awakenings are reiterated rather frequently, animals in the water tank are virtually in a permanent anxiety state even during deep SWS. The high level of emotional tension in the form of an after-effect persists in the animal for rather a long time in the postdeprivation period too. In spite of this it is namely at this time that the rebound of not only the deprived PS, but still more, of SWS is observed. On the basis of analysis of these facts it is concluded, that water tank method is not adequate for PSD. At the same time the character of the SWC course during the high emotional tension elicited by stressful factors is discussed. These data may also be beneficial while discussing the abundant controversial data accumulated in the literature concerning the effect of water tank PSD on the process of learning, as well as on the role of PS in the organization of memory in general.
Key Words: Sleep-wakefulness cycle, PS deprivation, SWS deprivation, water tank method, anxiety state.
Acknowledgments
This research was supported by the Japanese Government, under the ISTC grant G-391.
Correspondence: Oniani Tengiz, Prof.,
Department of Neurobiology of Sleep-Wakefulness Cycle,
I.S. Beritashvili Institute of Physiology, Georgian Academy of Sciences,
14, L. Gotua str., Tbilisi, 380060, Georgia.
E-mail: nswc@neurobiology.ge