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The physiological role of orexins
Lidia Martynska1, Ewa Wolinska-Witort, Magdalena Chmielowska
1Department of Clinical Neuroendocrinology, Medical Centre of Postgraduate Education, Warsaw, Poland. zncmkp@polbox.com
Neuro Endocrinology Letters
|September 2, 2005
Summary
Orexins (hypocretins) are brain peptides regulating sleep, appetite, and energy. Altered orexin neurotransmission and undetectable levels in cerebrospinal fluid are linked to narcolepsy.
Area of Science:
- Neuroscience
- Endocrinology
- Molecular Biology
Background:
- Orexins/hypocretins are neuropeptides synthesized in the hypothalamus.
- Orexin-A and orexin-B are key peptides acting on orexin receptors (OxR1 and OxR2).
- Their structure is conserved across mammals.
Purpose of the Study:
- To summarize the roles of orexins in physiological functions.
- To highlight the involvement of orexins in narcolepsy pathogenesis.
Main Methods:
- Review of existing literature on orexin/hypocretin neuropeptides.
- Analysis of orexin and receptor structures and functions.
- Examination of orexin's role in narcolepsy models and patients.
Main Results:
- Orexins regulate food intake, energy expenditure, neurohormone secretion, cardiovascular function, and sleep-wake cycles.
- Mutations in preproorexin or OxR2 receptor genes cause narcolepsy in animal models.
- Narcolepsy patients exhibit altered orexin neurotransmission and undetectable cerebrospinal fluid orexin levels.
Conclusions:
- Orexins are crucial for maintaining normal physiological functions, particularly sleep-wake regulation.
- Dysfunction in the orexin system is a primary cause of narcolepsy.
- Further research into the orexin system holds therapeutic potential for sleep disorders.