CORTICAL ACTIVATION STATES IN SLEEP AND ANESTHESIA - II - RESPIRATORYREFLEXES

Under urethane anesthesia, animals exhibit patterns of cortical activi ty similar to those seen in wake, drowsiness and slow-wave sleep in un anesthetized animals. In the present study, hypoxic and hypercapnic ve ntilatory reflexes were examined in unanesthetized and urethane-anesth etized golden mantled ground squirrels in states with similar EEG prof iles. Synchronized EEG patterns occurred less frequently in both unane sthetized and anesthetized animals during hypoxic (10% O-2) and hyperc apnic (5% CO2) exposure. Breathing frequency fell significantly during sleep in animals breathing all gas mixtures, while the relative venti latory sensitivity to hypoxia and hypercapnia increased during sleep. Urethane-anesthetized animals also showed significant falls in breathi ng frequency and ventilation and increases in relative ventilatory sen sitivity to hypoxia and hypercapnia as they moved into states with syn chronized EEG patterns. These data suggest that the brain activity sta tes observed under urethane anesthesia mimic sleep/wake in terms of th eir effect on respiratory function and that changes in breathing patte rn and the enhancement of ventilatory responses in states with a synch ronized EEG is not due solely to changes in levels of behavioural stim uli. (C) 1998 Elsevier Science B.V. All rights reserved.