Background: Increasing evidence has indicated that brain orexin plays a vital role in the regulation of gastrointestinal (GI) physiology such as gastric acid secretion and GI motility. The aim of this study was to elucidate the effects and mechanisms of orexin on gastric motility in non-fasted rats.
Methods: In this study, we recorded intraluminal gastric pressure waves in freely moving conscious rats with a manometric catheter located in the antrum. We assessed the area under the manometric trace as the motor index (MI), and compared its values for 1 h before and after drug administration.
Results: Intracisternal (ic) injection of orexin-A (10 μg) significantly increased the MI, but intraperitoneal (ip) injection did not have any effect. Pretreatment of ip injection of atropine significantly blocked the orexin-A-induced stimulation of gastric motility. Intravenous injection of 2-deoxy-D-glucose (2-DG, 200 mg/kg), a central vagal stimulant, significantly increased the MI. The ic injection of SB-334687 (40 μg), a selective orexin-A antagonist, did not modify the basal MI, but this antagonist significantly suppressed the stimulant action of 2-DG.
Conclusions: These results suggest that endogenous orexin-A in the brain is involved in the vagal-dependent stimulation of gastric contractions.