IMR Press / FBL / Volume 8 / Issue 6 / DOI: 10.2741/1159

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on as a courtesy and upon agreement with Frontiers in Bioscience.

Hypothalamic regulation of sleep and arousal
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1 Research Service, V.A. Greater Los Angeles Healthcare System, 16111 Plummer Street, North Hills, CA 91343
2 Department of Psychology, School of Medicine, University of California, Los Angeles, CA 90024
3 Department of Medicine, School of Medicine, University of California, Los Angeles, CA 90024

Academic Editor: James Krueger

Front. Biosci. (Landmark Ed) 2003, 8(6), 1074–1083;
Published: 1 September 2003
(This article belongs to the Special Issue Basic science of sleep)

The hypnogenic function of the rostral hypothalamic region, particularly the preoptic area (POA) was established previously on the basis of lesion, neuronal unit recording, and neurochemical and thermal stimulation studies. Recent studies have mapped the locations of putative sleep-promoting neurons in the POA using c-Fos immunostaining techniques and confirmed these findings with electrophysiological methods. Segregated groups of sleep-active neurons have been localized in the ventrolateral POA (vlPOA) and median preoptic nucleus (MnPN). MnPN and vlPOA sleep-active neurons express the inhibitory transmitter, GABA. In vlPOA neurons, GABA is co-localized with a second inhibitory transmitter, galanin. Descending projections from these sites terminate in putative arousal-promoting cell groups, including histaminergic, serotonergic, orexinergic, noradrenergic, and cholinergic neurons. These findings suggest the hypothesis that non-REM sleep occurs as a consequence of GABAergic and galaninergic inhibition of arousal-promoting neurons resulting from activation of vlPOA and MnPN sleep-promoting neurons. In support of this hypothesis, it was shown that putative sleep-promoting and arousal-promoting neurons exhibit reciprocal changes in discharge across the sleep-wake cycle and that GABA release in wake-promoting sites increases during nonREM sleep. In addition, some POA sleep-active neurons are warm-sensitive. Local POA warming inhibits discharge of multiple arousal-promoting neuronal groups. POA warming, unit recording, and lesion studies also show that POA regulates the amount of delta EEG activity within nonREM sleep, and index of the depth of sleep. Finally, there is evidence that arousal systems inhibit vlPOA and MnPN neurons and the POA hypnogenic mechanism. Mutually-inhibitory interactions between sleep-promoting and arousal-promoting systems are hypothesized to form a functional sleep-wake switch.

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