Effects of motilin in the hippocampus on the interdigestive migrating motor complex in rats

Objective:To explore the effects of motilin in the hippocampus on the interdigestive migrating motor complex (MMC) in rats. Methods: Adult SD rats of either sex were used; 0.5 μl motilin (0.74 mmol/L) was injected into the guide cannula which was stereotaxically implanted into the hippocampus previously. Then the MMC was recorded by a RM6240B multilead physiological recording system. Results: (1)MMC characteristics of normal rats’ duodenum: the frequency of phase Ⅲ was (18.1±0.4) bursts/min; the amplitude of phase Ⅲ was (260.5±42.3)μV; the duration of phase Ⅲ was (354.1± 21.6) s; MMC cycle duration was (690.2±58.7)s. (2) After motilin was injected into the hippocampus, the duodenal MMC cycle duration was decreased significantly. However, the amplitude of phase Ⅲ and the frequency of phase Ⅲ were increased. But there were no effects on the duration of phase Ⅲ. Frequency of phase Ⅲ percentage change was much more than amplitude of phase Ⅲ percentage change (57.2±2.8 vs 39.3±5.2). (3) Effects of motilin in the hippocampus on MMC were completely abolished by subdiaphragmal vagotomy. (4) Effects of motilin in the hippocampus on MMC were unaffected by intravenously injected atropine, phentolamine or propranolol. (5) The anti-motilin serum partly abolished the effects of motilin in the hippocampus on MMC. Conclusion: Motilin in the hippocampus has effects on the duodenal MMC cycle duration, the amplitude of phase Ⅲ and the frequency of phase Ⅲ. Motilin in the hippocampus plays an important role in duodenal MMC.