Abstract
The suprachiasmatic nucleus (SCN) temporally organizes behavior in part by sustaining arousal during the wake period of the sleep/wake cycle to consolidate adaptive waking behavior. In this study, we demonstrate direct projections from the SCN, in both the rat and the human brains, to perikarya and proximal dendrites of two groups of posterior hypothalamic neurons with axonal projections that suggest they are important in the regulation of arousal, one producing hypocretins (HCT) and the other melanin-concentrating hormone (MCH). In addition, we demonstrate that both HCT and MCH-producing neurons are immunoreactive for glutamate (GLU). These observations support the hypothesis that direct projections from the SCN to the posterior hypothalamus mediate the arousal function of the circadian timing system.
MeSH terms
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Amino Acid Sequence
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Animals
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Antibodies
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Arousal / physiology*
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Circadian Rhythm / physiology
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Female
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Glutamic Acid / physiology
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Humans
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Hypothalamic Hormones / analysis
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Hypothalamic Hormones / immunology
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Hypothalamus / chemistry
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Hypothalamus / cytology
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Hypothalamus / physiology
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Hypothalamus, Posterior / chemistry
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Hypothalamus, Posterior / cytology*
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Hypothalamus, Posterior / physiology*
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Intracellular Signaling Peptides and Proteins
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Male
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Melanins / analysis
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Melanins / immunology
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Molecular Sequence Data
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Neural Pathways
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Neuropeptides / analysis
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Neuropeptides / chemistry
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Neuropeptides / immunology
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Orexins
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Pituitary Hormones / analysis
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Pituitary Hormones / immunology
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Rabbits
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Rats
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Rats, Sprague-Dawley
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Sleep / physiology
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Suprachiasmatic Nucleus / chemistry
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Suprachiasmatic Nucleus / cytology*
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Suprachiasmatic Nucleus / physiology*
Substances
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Antibodies
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Hypothalamic Hormones
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Intracellular Signaling Peptides and Proteins
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Melanins
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Neuropeptides
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Orexins
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Pituitary Hormones
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Glutamic Acid
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melanin-concentrating hormone