Orexin neurons as arousal-associated modulators of central cardiorespiratory regulation.

Arousal level and metabolic demand is minimal during sleep, increases during quiet wakefulness, and further increases during active wakefulness phenomena such as exercise, stress, or panic. We summarize here our recent finding and relevant evidence showing possible contribution of orexin, a hypothalamic neuropeptide, to the state-dependent adjustment of central cardiorespiratory regulation. Orexin neurons seem to be a pivotal link between conscious and unconscious brain functions.