Conference of Biological Psychiatry

«Stress and Behavior»

Proceedings of the 9th International Multidisciplinary Conference «Stress and behavior» Saint-Petersburg, Russia, 16-19 May 2005 Editor: Allan V. Kalueff, PhD



E.V. Verbitsky Kogan Research Institute for Neurocybernetics,

Rostov State University, Rostov-on-Don, Russia

Cyclic organization of sleep reflects evolutionary perfection of adaptation of warm-blooded animals, especially superior mammals, to the periodic changes in their environment (Rotenberg, 1982; Kovalzon, 1993; Kovalzon, Verbitsky, 2003). Despite the fact that these organisms demonstrate the regular daily alternation of three states: slow wave sleep, REM-sleep and wakefulness, the character of their sleep can substantially vary even within the same species. This variation depends on both the specific habitat and a number of other factors (Pastukhov, 1986; Kovalzon, 1999; Jouvet, 2000; Lyamin, 2002). Additionally, the sleep in humans and animals can be affected by the environmental stimuli. For example, it can be reorganized under real or potentially threatening conditions (Ajrapetjanz, Vejn, 1992; Levin et al., 2001; 2003). Therefore, an in-depth assessment of sleep in organisms able to perceive novel conditions as potentially threatening, i.e. having a high level of trait anxiety, may be interesting. Electrophysiological and other indices of sleep were registered in adult rabbits and cats (mostly males) by polysomnographs SAGURA-2000 and LEONARDO. All the animals were divided into groups with high and low anxiety level (Verbitsky, 2003): high anxiety (7 rabbits, 6 cats); low anxiety (9 rabbits, 8 cats). By chronically implanted epidural EKoG, EOG and neck EMG electrodes, the cycles, the phases and the depth of sleep were recorded. The correlation of sleep episodes with the time of the day, typical sleep postures, peculiarities of alternation of behavioral forms during waking episodes preceding and following the sleep interval, as well as other indices were observed by video monitoring. During wakefulness, the intersystem interactions between cortical and subcortical structures were also analyzed (Verbitsky, 2004). Here we show that daily variability of sleep episodes in anxious animals was higher than in non-anxious subjects. The larger variability was more prominent during morning and evening periods, characterized by quick change of ambient light. Moreover, these animals had higher relative representation of deep sleep and much more micro-activations of different nature in its episodes. The relative representation of REM sleep in high anxiety animals also tended to increase. These differences in sleep are related to the character of inter-system interactions during wakefulness, where influences from the frontal cortex on another cortical regions and subcortical structures (both hypothalamus, non-specific thalamus, and the center of motor control — caudate nucleus) have a priority. The data obtained are considered in close connection with sleep differences in healthy people, for which the high anxiety group was often characterized by insomnia-like changes of the night sleep (Kovrov, 1999; Levin, Kovrov, 2003; Kovrov, Vejn, 2004). Additionally, the influences of stressors as sourses of anxiety could provoke the same changes at the initial stages of their action (Murtazaev et al., 1985; Posokhov, 1985; Levin et al., 2003). Taking into account the results of analysis of inter-systemic interactions between the cerebral structures during wakefulness, we may suggest that high anxiety organisms show higher activation of the brain. At the same time, the frontal cortical area suppresses the activity of synchronizing mechanisms of the thalamus and other structures, which is revealed not only in wakefulness, but also during the increase of slow wave sleep, and apparently weakens the interactions between thalamic pacemakers of sigma-spindles (Verbitsky, 2005). All these observations may explain both high impulsivity of behavior of high anxiety organisms and their characteristic alternation of episodes of high lability and relatively quiet state, even to

ISSN 1606-8181

the «freezing» reaction in the course of orienting behavior and other characteristic features (Kalueff, 2002, 2004). Thus, the characteristic features of sleep and wakefulness in high anxiety organisms as compared to low anxiety ones could be based on peculiarities of intersystem interactions between cerebral structures, including cortico-cortical and cortico-subcortical relationships, with influences from the frontal cortex on another cerebral regions having greater priority. These processes, in turn, are reflected both in the decrease of synchronization during sleep and suppression of activity of motor control center during wakefulness.

ISSN 1606-S1S1