Objectives:To investigate the effect of motilin on spontaneous afferent nerve discharge and gastric distention-induced afferent nerve discharge and explore the corresponding mechanism. Methods:Experiments were performed in anestherized SD rats. The sensory impulses of subdiaphragmatic vagal nerve were recorded by the RECORDER. Different dosages of motilin were intravenous injection. Some rats were pretreated with ondansetron and atropine, and then injected high-dose motlin. Results:Intravenous low motilin(1 μg/kg) had no effect, and intravenous medium and high motilin(5 μg/kg and 40 μg/kg respectively) caused obvious increase of spontaneous afferent discharge and gastric distention-induced afferent discharge. Pretreatment with ondansetron almost completely blocked the effects of motilin. Atropine had no obvious influence with the effect of high-dose motilin. Ondansetron inhibited afferent nerve discharge by itself,and atropine also did, but it failed to reach statistical significance. Conclusion:Motilin can excite spontaneous afferent nerve discharge and gastric distention-induced afferent nerve discharge. Vagal afferent nerve may play an important role in motilin transferring gastrointestinal information, 5-HT3 receptor are probably involved in the effect, but not atropine.