Hypoxic arousal in intact and carotid chemodenervated sleeping cats

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Abstract
To determine whether the carotid chemoreceptors or hyperpnea are required for arousal from sleep by hypoxia, 14 sleep-deprived cats were studied during slow-wave (SWS) and rapid-eye-movment (REM) sleep. Rapid hypoxia was produced by inhalation of 5% O2 in N2 or 6% CO in 40% O2 by intact cats and 5% O2 in N2 after carotid body denervation. Preliminary studies identified a period of SWS unassociated with spontaneous arousals. In 69 studies during SWS unassociated with spontaneous arousals, arterial O2 saturation (SaO2) values at arousal were: 47.1 .+-. 1.5% (mean .+-. SE) (5% O2, intact); 48.9 .+-. 1.4% (6% CO, intact); and 49.9 .+-. 2.0% (5% O2, denervated). During SWS associated with spontaneous arousals, SaO2 values at arousal were 71.6 .+-. 1.8% (5% O2, intact). Arousal from REM occurred at significantly lower values: 31.7 .+-. 3.9% (6% CO, intact) and 43.5 .+-. 2.3% (5% O2, intact). During both SWS and REM, inhalation of 5% O2 by intact animals caused a substantial increase in ventilation while 6% CO did not. More severe hypoxia is required for arousal from SWS when studies are done in a period unassociated with spontaneous arousals than from SWS associated with spontaneous arousals. Hypoxic arousal does not appear to require activation of the carotid bodies or hyperpnea. Implications for sleep associated apnea and hypopnea in humans were discussed.