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Orexin (/ ɒ ˈ r ɛ k s ɪ n /), also known as hypocretin, is a neuropeptide that regulates arousal, wakefulness, and appetite. [5] It exists in the forms of orexin-A and orexin-B.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 ...
Once made, the orexin peptides can bind to the orexin receptor; which is a G protein-coupled receptor. This receptor senses molecules outside the cell and activates inside signal transduction pathways to elicit cellular responses. Research shows that an absence of orexin-A appears to cause narcolepsy. Deficit amounts of orexin-A will make ...
Both orexin receptors exhibit a similar pharmacology – the 2 orexin peptides, orexin-A and orexin-B, bind to both receptors and, in each case, agonist binding results in an increase in intracellular calcium levels. However, orexin-B shows a 5- to 10-fold selectivity for orexin receptor type 2, whilst orexin-A is equipotent at both receptors ...
The neurotransmitter glutamate and the endocannabinoids (e.g., anandamide) and the orexin neuropeptides orexin-A and orexin-B are the primary signaling neurochemicals in orexin neurons; [3] [4] [7] pathway-specific neurochemicals include GABA, melanin-concentrating hormone, nociceptin, glucose, the dynorphin peptides, and the appetite ...
The endogenous orexin neuropeptides, orexin A and orexin B, are involved in the regulation of sleep–wake cycles and act to promote wakefulness. [33] [16] [7] Deficiency of orexin signaling is thought to be the primary cause of the sleep disorder narcolepsy. [33] [16] Disturbances in orexin signaling may also be involved in insomnia. [33]
An orexin receptor antagonist, or orexin antagonist, is a drug that inhibits the effect of orexin by acting as a receptor antagonist of one (selective orexin receptor antagonist or SORA) or both (dual orexin receptor antagonis or DORA) of the orexin receptors, OX 1 and OX 2. [1] Medical applications include treatment of sleep disorders such as ...
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The orexin 1 receptor (OX 1), is a G-protein coupled receptor that is heavily expressed in projections from the lateral hypothalamus and is involved in the regulation of feeding behaviour. OX 1 selectively binds the orexin-A neuropeptide. It shares 64% identity with OX 2. [5]