Blood pressure and heart rate changes during para-sleep in vagotomized and atropinized cats

Abstract

Blood pressure and heart rate changes were studied during para-sleep in unrestrained, unanesthetized cats. As has been previously reported in the cat, the onset of para-sleep was usually accompanied by a tonic decrease in blood pressure, and during the course of para-sleep phasic increases were also frequently observed. Heart rate, however, either increased or decreased with the onset of para-sleep, the change in a given animal being apparently dependent upon the preceding or baseline rate during ortho-sleep. After bilateral vagotomy, both blood pressure and heart rate showed a consistent decrease with the onset of para-sleep. The administration of methyl-atropine had the same effects. However, the transient increases in blood pressure, which were found to correspond to bursts of rapid eye movements, still persisted under these conditions. These findings suggest that sympathetic activity is tonically decreased and phasically increased during para-sleep.