A GABAergic pontine reticular system is involved in the control of wakefulness and sleep

The present work is the first in a series of studies designed to examine the role of a brainstem GABAergic system in the control of the behavioral states of sleep and wakefulness. GABA, muscimol (a GABAA receptor agonist) and bicuculline methiodide (a GABAA receptor antagonist) were microinjected, separately, into the nucleus pontis oralis (NPO) in three chronic, unanesthetized cats. The effects of these microinjections on the behavioral states of sleep and wakefulness were then examined. The injection of either GABA or muscimol induced wakefulness; quiet sleep and active sleep were suppressed. In contrast, the injection of bicucculline induced a prolonged state that was similar to naturally-occurring active sleep. These findings indicate the existence of GABAergic processes capable of controlling the activity of neurons within the NPO that are involved in the control of sleep and waking states. Specifically, these data suggest that cells within the NPO must be tonically inhibited by a GABAergic brainstem system in order for the state of wakefulness to be generated and maintained.