Neural circuitry responsible for sleep and wakefulness

Abstract

Research over the past 50 years has determined that specific neurons in the brain are responsible for generating waking, non-REM sleep, and REM sleep. Some of the neurons responsible for keeping us awake are also involved in regulating energy metabolism. One such arousal neuronal population contains the neuropeptide hypocretin, also known as orexin. The HCRT neurons are located in the hypothalamus, an area that also contains other neurons regulating energy metabolism. The hypocretin neurons are most active during waking and silent during sleep, and their activity has been shown to regulate brown adipose tissue (BAT) thermogenesis. The hypocretin neurons are also activated by low glucose levels and shut off when the glucose levels increase. Thus, the activity of the hypocretin neurons is linked to energy metabolism. Based on this relationship, it is easy to see how inadequate sleep or even frequent arousals during sleep, as occurs in obstructive sleep apnea, will affect energy metabolism and adiposity.