The Effect Of Lateral Ventricle Injection Of Orexin-A On Gastric Motility In Rats And Its Mechanism

Objective:To observe the effect and mechanism of intracerebroventricular(icv) injection of Orexin-A on gastric motility in rats.Methods:50 adult male rats were randomly divided into five groups, namely normal saline(NS), 1 ?g, 5 ?g, 10 ?g and 20 ?g Orexin(OXA)group. Two strain gauge transducers were attached on the antrum and duodenum to record circular muscle contractions. Spontaneous gastroduodenal contractions were recorded in freely moving conscious rats. Through icv injection of OXA, observed the changes in the gastrointestinal circular muscle motion waveform and duration in rats. 20 rats were randomly divided into two groups, one group with subcutaneous injection of NS + icv injection of 10?g OXA, another group with subcutaneous injection of atropine + icv injection of 10?g OXA, to observe the effects on gastrointestinal motility. Similarly selecting 10 rats were divided into sham group + 10?g OXA group, vagotomy + 10?g OXA group, which was used to elucidate the neural pathways of OXA. Then selecting 20 rats, first icv injection of NS then icv injection of OXA antagonist SB334867, observed the effect of endogenous OXA on gastrointestinal motility.Results: OXA(1–20 ?g) disrupted the interdigestive phase III-like contractions and induced an irregular postprandial-like motility pattern in the stomach and duodenum. The stimulatory effect of OXA on gastroduodenal postprandial-like motility pattern was abolished by atropine and truncal vagotomy(P<0.05). Central administration(icv) of selective OXA receptor antagonist, SB-334867(16 ?g), enhanced gastric spontaneous phase III-like contractions(P<0.05).Conclusions : Central administration of OXA changes GI motor pattern from interdigestive to postprandial via the vagal cholinergic pathways. Endogenous OXA may inhibit in interdigestive GI motility in rats.