Contribution of chemosensitive serotonergic neurons to interactions between the sleep-wake cycle and respiratory control

Abstract

Serotonergic neurons in the midbrain and medulla are sensitive to changes in serum CO2 concentrations. Medullary serotonergic neurons project to brainstem respiratory control centers and stimulate breathing. Midbrain serotonergic neurons project to thalamocortical circuitry responsible for sleep-wake modulation. There is state-dependent modulation of these medullary serotonergic neurons that may be responsible for state-dependent changes in respiratory rate and breathing regularity. Thus, with projections to both respiratory control centers and thalamocortical arousal circuits, chemosensitive serotonergic neurons are poised to induce both arousal and increased ventilation in response to potentially lifethreatening increases in PCO 2. This may have important implications for such clinical conditions as sudden infant death syndrome, obstructive sleep apnea, and panic disorder; disorders in which serotonin is thought to contribute to the underlying pathophysiology. © 2008 Birkhäuser Verlag AG.