Journal of Applied Physiology, Vol 80, Issue 6 2102-2107, Copyright © 1996 by American Physiological Society

ARTICLES

Effects of inspired gas on sleep-related apnea in the rat

J. Christon, D. W. Carley, D. Monti and M. Radulovacki
Department of Medicine, University of Illinois, Chicago 60612, USA.

Central apneas have been reported to occur in the rat during all stages of sleep. Two types of apnea have been described: spontaneous and postsigh, which are immediately preceded by an augmented breath. We studied the effect of inspired gas on the number and type of apneas in nine adult male Sprague-Dawley rats that were surgically prepared with cortical electroencephalogram and nuchal electromyogram electrodes. In addition to the electroencephalogram and electromyogram, we recorded respiration by the barometric method by using a single-chamber plethysmograph. Each rat was recorded from 1000 until 1600 on 4 separate days by using different inspired gases: room air, 100% O2, 15% O2, and 5% CO2. We found that the sleep-related apnea index was significantly higher during 100% O2 compared with room air (P < 0.05) and was significantly lower during 15% O2 and 5% CO2 compared with room air (P < 0.05). Postsigh apneas occurred more frequently than did spontaneous apneas (P < 0.0001). The coupling between sighs and apneas was strengthened by hyperoxia and weakened by hypoxia and hypercapnia (P < 0.05 for each). We conclude that stimulation of chemoreceptors acts to oppose apnea in the rat.

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