Objective To determine the effect of the area postrema (AP) of the medulla oblongata on ga strointestinal interdigestive migrating motor complex (MMC) and the plasma motil in level. Methods Interdigestive MMC activities of the antrum and duodenum were recorded by strain gauge implanted on the serosa of 8 conscious dogs. A cannula was intubated in femoral vein for motilin injection. The plasma motilin concentration was measur ed by RIA. We observed: (1) normal interdigestive MMC activity and fluctuatio ns in plasma motilin concentration; (2) the effects of electrically damaging the AP on MMC activity and plasma motilin level; (3) whether intravenous injection of motilin could induce phase Ⅲ contractions after the AP was destroyed. Results (1) Typical interdigestive MMC with phase Ⅰ, Ⅱ, Ⅲ, and Ⅳ was recorded in nor mal dogs. Phase Ⅲ was concurrent with the peak of plasma motilin level. (2) I n damaged AP dogs, antroduodenal interdigestive MMC contractions were suppressed ; cyclic, phasic and migratory pattern of MMC was disrupted. Plasma motilin con centration was decreased. Intravenous injection of motilin could not induce pha se Ⅲ contractions.Conclusions The area postrema might play an important role, which is mediated by motilin, on the regulation of interdigestive MMC. Objective To determine the effect of the area postrema (AP) of the medulla oblongata on ga strointestinal interdigestive migrating motor complex (MMC) and the plasma motil in level. Methods Interdigestive MMC activities of the antrum and duodenum were recorded by strain gauge implanted on the Serum of 8 conscious dogs. A cannula was intubated in femoral vein for motilin injection. The plasma motilin concentration was measur ed by RIA. We observed: (1) normal interdigestive MMC activity and fluctuatio ns in plasma motilin concentration; (2) the effects of electrically damaging the AP on MMC activity and plasma motilin level; (3) whether intravenous injection of motilin could induce phase Ⅲ contractions after the AP was destroyed. Results (1) Typical interdigestive MMC with phase Ⅰ, Ⅱ, Ⅲ, and Ⅳ was recorded in nor mal dogs. Phase III was concurrent with the peak of plasma motilin level. (2) I n damaged AP dogs, antroduodenal interdigestive MMC contractions were suppressed; Cyclic, phasic and migratory pattern of MMC was disrupted. Plasma motilin con centration was decreased. Intravenous injection of motilin could not induce pha se III contractions. Conclusions The area postrema might play an important role, which is mediated by motilin, on the regulation of interdigestive MMC.