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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 ...
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.
Narcolepsy is a chronic neurological disorder that impairs the ability to regulate sleep–wake cycles, and specifically impacts REM (rapid eye movement) sleep. [1] The pentad symptoms of narcolepsy include excessive daytime sleepiness (EDS), sleep-related hallucinations, sleep paralysis, disturbed nocturnal sleep (DNS), and cataplexy. [1]
Cataplexy manifests itself as muscular weakness which may range from a barely perceptible slackening of the facial muscles to complete muscle paralysis with postural collapse. [7] Attacks are brief, most lasting from a few seconds to a couple of minutes, and typically involve dropping of the jaw, neck weakness, and/or buckling of the knees.
This may also be called standard range. In contrast, optimal (health) range or therapeutic target is a reference range or limit that is based on concentrations or levels that are associated with optimal health or minimal risk of related complications and diseases. For most substances presented, the optimal levels are the ones normally found in ...
Orexin receptor type 2 (Ox2R or OX 2), also known as hypocretin receptor type 2 (HcrtR2), is a protein that in humans is encoded by the HCRTR2 gene. [5] It should not be confused for the protein CD200R1 which shares the alias OX2R but is a distinct, unrelated gene located on the human chromosome 3.
The rhesus monkeys were split into a test group and into a control group. The test group was administered orexin-A, intravenously or nasally. The control group was given a placebo. The sleep-deprived monkeys which were given the nasal form of orexin-A performed far better than the ones treated with injections.
In individuals with normal carbohydrate metabolism, insulin levels rise concordantly to drive glucose into the body's tissues and maintain blood glucose levels in the normal range. [10] Insulin stimulates the uptake of valine , leucine , and isoleucine into skeletal muscle , but not uptake of tryptophan .