Role of a novel neurppeptide, orexin,in the central regulation of gastric acid secretion

我们首先检查了脑池内注射食欲素-A对大鼠胃酸分泌的影响。通过幽门结扎法，脑池内注射食欲素A剂量依赖性地刺激胃酸分泌。相反，腹膜内施用食欲素-A不能刺激胃酸分泌，表明食欲素-A在脑中起作用以刺激胃酸分泌。在迷走神经切断大鼠中未观察到胃分泌的刺激，表明迷走神经介导食欲素诱导的酸分泌食欲素-A是由33个氨基酸组成的神经肽，具有两个链内二硫键，即Cys 6-Cys 12和Cys 7-Cys 14。而食欲素B是一种由28个氨基酸组成的肽，不含二硫键，对胃酸无刺激作用。在幽门结扎的清醒大鼠中，脑池内注射食欲素-A而不是食欲素-B或不含两个二硫键的食欲素-A（15-33）刺激胃酸分泌。能力 ...更多信息 [Ala 6，12]orexin-A、[Ala 7，14]orexin-A和[Ala 6，7，12，14]orexin-A对胃酸分泌的刺激作用均小于orexin-A。Orexin-A以剂量依赖性方式诱导CHO-K1/OX 1 R细胞内[Ca 2 +]i瞬时升高。食欲素-A、食欲素-B或食欲素-A（15-33）的OX 1 R的EC 50值分别为0.068、0.69或4.1 nM，表明不含二硫键的肽对受体的效力较低。与orexin-A相比，具有一个或两个二硫键修饰的三种orexin-A类似物对OX 1 R的激动活性显著降低。Orexin-A和Orexin-B对OX 2 R的EC 50值几乎相等，但对Orexin-A（15-33）和三个丙氨酸取代的Orexin-A的受体的效力小于Orexin-A。观察到胃酸排出量与OX 1 R而非OX 2 R的EC 50值之间存在显著的负相关关系。这些结果表明，食欲素-A诱导的酸刺激需要OX 1 R激活，食欲素-A中的二硫键可能在受体激活中起关键作用。少

We examined first the effect of intracisternal injection of orexin-A on gastric acid secretion in rats. Intracisternal injection of orexin-A dose-dependently stimulated gastric acid output by the pylorus-ligation method. In contrast, intraperitoneal administration of orexin-A failed to stimulate acid, secretion, suggesting that orexin-A acts in the brain to stimulate gastric acid secretion. The stimulation of gastric secretion was not observed in the vagotomyzed rats, indicating that the vagus nerve mediates the orexin-induced acid secretion Orexin-A is a neuropeptide consisting 33 amino acids with two intrachain disulfide bonds, namely Cys6-Cys12 and Cys7-Cys14. In contrast, orexin-B, a peptide containing 28 amino acids without disulfide bond, which has no stimulatory action of gastric acid. Intracisternal injection of orexin-A but not orexin-B or orexin-A (15-33) that does not contain both disulfide bonds stimulated gastric acid secretion in pylonis-ligated conscious rats. The abilit … More y of the stimulation of gastric acid output was less in three alanine-substituted orexin-A, [Ala 6, 12]orexin-A, [Ala 7, 14]orexin-A and [Ala 6, 7, 12, 14]orexin-A, than orexin-A, Orexins-induced calcium increase was measured in CHO-K1 cells expressing OX1R or OX2R. Orexin-A induced a transient increase in [Ca2+]i in CHO-K1/OX1R cells in a dose-dependent manner. EC50 values for OX1R of orexin-A, orexhi-B or orexin-A (15-33) was 0.068, 0.69 or 4.1 nM, respectively, suggesting that peptides containing no disulfide bonds have lower potency for the receptor. Agonistic activity for OX1R of the three orexin-A analogues with modification of one or both disulfide bonds was significantly reduced as compared with that of orexin-A. EC50 values for OX2R of orexin-A and orexin-B was almost equal but potency for the receptor of orexin-A (15-33) and three alanine substituted orexin-A was less than that of orexin-A. A significant inverse relationship between gastric acid output and EC50 values for OX1R but not OX2R was observed. These results suggested that the orexin-A-induced acid stimulation requires OX1R activation and that disulfide bonds in orexin-A may have a key role in the receptor activation. Less