Extrinsic Orexin-A in Lateral Hypothalamic Area Regulates Gastric Motility in Rats

Abstract

Abstract:The orexin neuropeptide family consists of orexin-A and orexin-B, which are coded from the same prepro-mRNA. Although peripherally administered orexin-A abolishes small intestinal interdigestive contractions in rats, it still remains unclear whether orexin-A of lateral hypothalamic area(LHA) effects on the gastric motility in rats. We selected Wistar rats as our subjects. A stainless-steel injection cannula was implanted unilaterally into the LHA. A force transducer was embedmented into the stomach to record circular muscle contractiontions in freely moving conscious rats. The gastric motility was monitored by administration of ghrelin into LHA. The changes of amplitude of constriction and frequency of gastric motility were monitored in conscious rats by a transducer. Subdiaphragmatic vagotomy was performed to elucidate the neural pathways of orexin-A. After microinjection of orexin-A into LHA 5-20 min later, Orexin-A dose-dependently increased the amplitude of contraction and accelerated frequency of gastric motility in the stomach. The effect of orexin-A on promoting the amplitude and frequency of gastric contraction disappeared after 0.5μg orexin-A +6.0μg SB-334867 mixture was microinjection into LHA. However, there was no significant changes of amplitude and frequency of gastric contraction while injection of orexin-A receptor antagonists SB-334867 alone. The stimulatory effect of orexin-A on gastric motility was abolished by subdiaphragmatic vagotomy. It is suggested that exogenous orexin-A of LHA may promote gastric motility, the effect may be accomplished through the LHA-vagus pathway.