In chronic experiments on cats, using the recording of local blood flow in different regions of the hypothalamus in the sleep-wakefulness cycle, it was found that during paradoxical sleep, the level of local blood flow in the posterior hypothalamus increased significantly, while at the same time in the anterior hypothalamus and in the preoptic region a sharp reduction takes place in local blood flow. In deep slow wave sleep the opposite pattern is observed: the level of local blood flow increases in the anterior hypothalamus and in the preoptic region, and decreases in the posterior hypothalamus. The conclusion is drawn that in one and the same sleep phase the diverse directionality of the changes in the level of local blood flow in the different regions of the hypothalamus must be associated with functional shifts in these structures, and the functional state of each of them in different phases of the sleep-wakefulness cycle is evaluated on the basis of this.
The aim of this study was revealing the temperature changes in rats' brain tissue caused by whole body hyperthermia. The analysis of received results allows to conclude that the brain has a highly secured system of temperature autoregulation against the exogenous temperature changes. The upper limit of this autoregulation (for rats, at least) is in the range of 45 ∘ C of environment. An important role in the normal functioning of the brain temperature autoregulation system belongs to Nitric Oxide. The behavioral disorders, observed in animals after whole body hyperthermia (sure within the range of brain temperature autoregulation) are hardly associated with the changes in temperature of the Central Nervous System, but rather have to be mediated by impaired blood circulation and oxygen supply to the brain tissues, caused by the rapid deterioration of the blood rheological properties.
It was found in chronic experiments in cats, using the recording of local blood flow and oxygen tension (pO2) in the anterior and posterior hypothalamus in the sleep-wakefulness cycle, that when the phases of sleep are alternated, the changes in these parameters are in different directions: the level of blood flow and the frequency of fluctuation of the pO2 during paradoxical sleep increase in the posterior hypothalamus, while they decrease in the anterior hypothalamus. On the other hand, the opposite pattern is observed during slow-wave sleep. The multidirectionality of the changes in local blood flow level and in the frequency of fluctuations of pO2 in one and the same sleep phase indicate that they are of local origin and must be governed by functional-metabolic shifts in these structures; the functional state of the posterior hypothalamus during paradoxical sleep is assessed on this basis.
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