Orexin B (human), a 28-residue peptides, has affinity for the OX1 and OX2 receptor with Ki of 420 and 36nM, respectively[1].
Orexin B induces depolarization in both type 1 and type 2 neurons of the PVN with dose-dependent, and the changes in membrane potential are larger in type 2 neurons than in type 1[2]. Orexin B can inhibit the uptake of fAβ in BV2 cell line, reducing the levels of p-p38, p-Akt, and PI3K[3].
Orexin B was acutely administered into the lateral ventricle of male rats through preimplanted indwelling catheters, Orexin B significantly augmented food intake; at the 2h time point, observed 5-and 12-fold stimulation of food consumption by 3nmol and 30nmol Orexin B, respectively, as compared with vehicle controls[4]. Orexin B will be rapidly degraded in blood, so no 125I-Orexin B could be detected in intact form in brain when injected peripherally in male albino ICR mice at a dose of 6pmol/mouse through the isolated left jugular vein[5].
References:
[1] Smart D. Orexins: a new family of neuropeptides[J]. British journal of anaesthesia, 1999, 83(5): 695-697.
[2] Shirasaka T, Miyahara S, Kunitake T, et al. Orexin depolarizes rat hypothalamic paraventricular nucleus neurons[J]. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2001, 281(4): R1114-R1118.
[3] An H, Cho M H, Kim D H, et al. Orexin impairs the phagocytosis and degradation of amyloid-β fibrils by microglial cells[J]. Journal of Alzheimer’s Disease, 2017, 58(1): 253-261.
[4] Sakurai T, Amemiya A, Ishii M, et al. Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior[J]. Cell, 1998, 92(4): 573-585.
[5] Kastin A J, Akerstrom V. Orexin A but not orexin B rapidly enters brain from blood by simple diffusion[J]. The Journal of pharmacology and experimental therapeutics, 1999, 289(1): 219-223.
Orexin B (human)是一种由28个氨基酸残基组成的肽，对OX1和OX2受体具有亲和力，Ki值分别为420nM和 3nM[1]。
Orexin B呈剂量依赖性地诱导室旁核（PVN）的1型和2型神经元发生去极化，并且2型神经元的膜电位变化大于1型神经元[2]。Orexin B能够抑制BV2细胞系对纤维状β淀粉样蛋白（fAβ）的摄取，降低p-p38、p-Akt和PI3K的水平[3]。
Orexin B急性注入雄性大鼠的侧脑室能够显著增加食物摄入量；在注射后2h的时间点，与对照组相比，3nmol和30nmol的Orexin B分别使食物消耗量增加了5倍和12倍[4]。Orexin B在血液中会迅速降解，每只雄性白化ICR小鼠 6pmol的剂量进行外周注射时，在小鼠大脑中无法检测到完整形式的125I标记的Orexin B[5]。