Orexin

Orexins, also known as hypocretins, are two neuropeptides secreted from orexin-containing neurons, mainly in the lateral orexin LH.

Orexin neurons receive a variety of signals related to environmental, physiological and emotional stimuli, and project broadly to the entire CNS. Furthermore, a dysfunction of orexinergic system may underlie different pathological conditions. A selective loss orexin neurons was found in narcolepsia, supporting the crucial role of orexins in maintaining wakefulness. In animal models, orexin deficiency lead to obesity even if the consume of calories is lower than wildtype counterpart. Reduced physical activity appears the main cause of weight gain in these models resulting in energy imbalance. Interestingly, orexinergic neurons show connections to regions involved in cognition and mood regulation, including hippocampus.

Orexin

Federal government websites often end in. The site is secure. Preview improvements coming to the PMC website in October Learn More or Try it out now. The hypothalamus monitors body homeostasis and regulates various behaviors such as feeding, thermogenesis, and sleeping. Orexins also known as hypocretins were identified as endogenous ligands for two orphan G-protein-coupled receptors in the lateral hypothalamic area. For example, orexin neurons are regulated by peripheral metabolic cues, including ghrelin, leptin, and glucose concentration. This suggests that they may provide a link between energy homeostasis and arousal states. A link between the limbic system and orexin neurons might be important for increasing vigilance during emotional stimuli. Orexins are also involved in reward systems and the mechanisms of drug addiction. These findings suggest that orexin neurons sense the outer and inner environment of the body and maintain the proper wakefulness level of animals for survival. The hypothalamus plays a critical role in maintaining energy homeostasis by coordinating behavioral, metabolic, and neuroendocrine responses Bernardis and Bellinger, Within this region, the lateral hypothalamic area LHA has been regarded as an important center for feeding and arousal because animal models with LHA lesions exhibit hypophagia and decreased arousal that frequently leads to death. Orexin A and orexin B also known as hypocretin 1 and hypocretin 2 are neuropeptides expressed exclusively by LHA neurons.

Sleep neurobiology from a clinical perspective. Zeitzer, J. Viggiano, orexin, A.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. A Corrigendum to this article was published on 20 October Orexins are lateral hypothalamic neuropeptides that have a highly important role in the regulation of wakefulness.

Federal government websites often end in. The site is secure. Preview improvements coming to the PMC website in October Learn More or Try it out now. Orexins, also known as hypocretins, are two neuropeptides secreted from orexin-containing neurons, mainly in the lateral hypothalamus LH.

Orexin

The most common form of narcolepsy , type 1, in which the individual experiences brief losses of muscle tone "drop attacks" or cataplexy , is caused by a lack of orexin in the brain due to destruction of the cells that produce it. There are 50,—80, orexin-producing neurons in the human brain, [8] located predominantly in the perifornical area and lateral hypothalamus. Orexin was discovered in almost simultaneously by two independent groups of researchers working on the rat brain. Luis de Lecea, Thomas Kilduff , and colleagues reported the discovery of the hypocretin system at the same time as Takeshi Sakurai from Masashi Yanagisawa 's lab at the University of Texas Southwestern Medical Center at Dallas reported the discovery of the orexins to reflect the orexigenic appetite-stimulating activity of these peptides. In their paper describing these neuropeptides, they also reported discovery of two orexin receptors, dubbed OX 1 R and OX 2 R. The two groups also took different approaches towards their discovery. One team was interested in finding new genes that were expressed in the hypothalamus. In , scientists from the Scripps Research Institute reported the discovery of several genes in the rat brain, including one they dubbed "clone They cloned this DNA and studied it using electron microscopy.

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Functional magnetic resonance imaging reveals different neural substrates for the effects of orexin-1 and orexin-2 receptor antagonists. Responses to corticotropin-releasing hormone in the hypercorticolism of depression and Cushing's disease. Strong innervation of the caudal region of the sacral cord suggests a role in the regulation of both sympathetic and parasympathetic functions. Interestingly, physical exercise produces an increase of orexin-A level in cerebrospinal fluid of rats, dogs and cats, and in plasma of humans Messina G. To test our hypothesis, we first sought to determine if acute activation of presynaptic Ox inputs Ox terminals within the VLPO could trigger behavioral and electroencephalographic arousal from sleep. They are adaptations that prepare an animal to cope with an emergency, and specifically to perform the extreme muscular exertion of flight or attack. Harada et al. Watabe-Uchida, M. Wong, K. The role of orexin in motivated behaviours. Therefore, it is important to know the distribution pattern of orexin receptors to identify the functional neuronal network.

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Sleep 11 , 1—16 Hypocretin orexin deficiency in human narcolepsy. Basal forebrain control of wakefulness and cortical rhythms. Leonard, C. Neurons containing orexin in the lateral hypothalamic area of the adult rat brain are activated by insulin-induced acute hypoglycemia. Charney DS. Kowalczyk, M. Wikimedia Commons has media related to Orexin. Narcolepsy in orexin knockout mice: molecular genetics of sleep regulation. In particular, noradrenergic neurons of the LC, dopaminergic neurons of the ventral tegmental area VTA , and histaminergic neurons of the TMN are activated by orexins Hagan et al. Dehkordi, O.