Temperature changes in the rabbit brain during paradoxical sleep

Abstract

To clarify functional and metabolic conditions in the brain during paradoxical sleep as compared with slow wave sleep and alertness, simultaneous recordings were made of brain temperature, cortical and subcortical EEG, and DC potential shifts, together with the local temperatures of such organs as the liver and uterus, and the skin of the neck. Blood flow in the ipsilateral common carotid artery was also measured in five rabbits. The following results were obtained: 1. 1. During paradoxical sleep the temperature of the brain rose very markedly (0.1–0.4°C). The temperature of the cortex was lower than that of the brain-stem but the two regions showed parallel shifts. 2. 2. The elevation of brain temperature associated with an arousal reaction without vigorous body movements was usually considerably less than the elevation during sustained paradoxical sleep. 3. 3. During the slow wave sleep stage the temperature of the brain usually dropped but before the arousal reaction appeared, a gradual temperature elevation was often observed. In some cases the temperature rose slightly even during the slow wave stage of sleep. 4. 4. During paradoxical sleep the temperatures of the neck skin, uterus and liver failed to show elevations parallel with that of the brain temperature. 5. 5. Measurements of blood flow in the common carotid artery revealed that, although there were some phasic increases, no definite increase in average level of blood flow occurred during paradoxical sleep over that of the preceding stage of slow wave sleep. There was no evidence that the elevation in brain temperature during paradoxical sleep was due to warming by increased flow of arterial blood of a higher temperature than that of the brain and it was concluded that the cause of elevation in brain temperature was increased metabolic activity in the forebrain.