Changes of brain pO2 during paradoxical sleep in cats☆

Abstract

Cats were chronically implanted with polarographic cathodes in different regions of the brain to record the local oxygen concentration or pressure. The cortical electrical activity, the electromyogram of the neck muscles and the eye movements were also recorded as indicators of wakefulness and slow paradoxical sleep. Animals were studied in unrestrained conditions during these behavioural states. In every experiment the oxygen-dependance of polarographic electrodes was tested by changing the oxygen concentration in the inhaled gases. During paradoxical sleep phasic pO 2 changes were observed in some nuclear structures characterized by a dramatic increase in the amplitude of oscillations. These changes were found in a number of subcortical and brain stem regions (Table 1) and were never observed in the neo and archicortex, in the specific thalamic nuclei or in the white matter. Increased brain pO 2 oscillations constitute an indicator of the PS just as good or better than the electrocortical activation or the electromyogram. In some cases they heralded the PS. The changes observed in the pO 2 during the PS differed from those recorded during arousal and alertness because in the two latter situations they extended to all of the brain areas studied. It is postulated that these variations be due to a local increase of neuronal activity.