The distribution of motilin receptor in the amygdala of rats and its role in migrating myoelectric complex

Objective:To investigate the distribution of the motilin receptor in the amygdala of rats and its role in regulating the duodenal migrating myoelectric complex(MMC).Methods:The distribution of motilin receptor in the amygdala in adult SD rats was detected by immunohistochemistry methods,and the duodenal interdigestive MMC was recorded via the electrodes implanted in the duodenum and analyzed us- ing a multichannel recorder.Results:Motilin receptor was observed in the amygdala of rats.The great amount of motilin receptor was found in the medial amygdaloid nucleus,which was also abundant in the basolateral nucleus but less abundant in the basomedial amygdaloid nucleus,the central amygdaloid nucle- us and the lateral amygdaloid nucleus.The shortening of the duodenal MMC cycle duration and the in- crease of the amplitude and the frequency of phase $ were recorded after motilin receptors being bound with exogenous motilin in the amygdala.The effects could be completely blocked by the subdiaphragmatic vagotomy but not by the intravenous injections of atropine,phentolamine or propranolol.Anti-motilin serum could partially block these effects,and the destruction of the basolateral nucleus of the amygdala had no significant effects on the duodenal MMC.Conclusion:Motilin receptor is present in all the subnu- clei of the amygdala,with the greatest amount of motilin receptor present in the medial amygdaloid nucle- us.Microinjections of motilin in the amygdala can shorten the duodenal MMC cycle duration and increase the amplitude and the frequency of phaseⅢ.These effects might be accomplished via the amygdala-hy- pothalamus-brainstem-vagus pathway,indicating the important role of the amygdala motilin receptor in the duodenal MMC regulation.

Relationship between entero-hepatic bile acid circulation and interdigestive migrating myoelectrical activity in rats

AIM： To investigate the effects of entero-hepatic bile add circulation on the inter-digestive migrating myoelectrical complex （MMC） in rats. METHODS： Thirty-two rats were divided into four groups. Three pairs of bipolar silver electrodes were chronically implanted in the antrum, duodenum and jejunum. Three groups of Uhem were ligatecl around the upper part of common bile duct （CBD）. The experiments were performed in consdous and fasting state. The gastrointestinal myoelectrical activity was recorded. Ursodeoxycholic acid （UDCA） and saline were then perfused into stomachs of two groups with CBD obstruction and the effects of them on the MMC were observed. RESULTS： A typical pattern of MMC was observed in normal fasting rats. MMC of antral and duodenal origin disappeared temporarily in earlier stage of CBD obstruction. While MMC of jejunum origin appeared. increased MMC cycle duration was seen after 4 d in rats with CBD obstruction. The MMC after CBD obstruction was characterized by an increased duration of phase Ⅱ-like activity and decreased duration of phase Ⅰ ＆ Ⅲ activity. Perfusion into stomachs with UDCA resulted in a shorter MMC cycle duration and a longer duration of phase III of duodenal origin compared to the normal group. CONCLUSION： Entero-hepatic bile add drculation initiates inter-digestive MMC of duodenal origin.

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 retool/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. Resuits： （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.

Role of the area postrema of medulla oblongata in the regulation of canine interdigestive migrating motor complex

OBJECTIVE: To determine the effect of the area postrema (AP) of the medulla oblongata on gastrointestinal interdigestive migrating motor complex (MMC) and the plasma motilin 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 measured by RIA. We observed: (1) normal interdigestive MMC activity and fluctuations 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 normal dogs. Phase III was concurrent with the peak of plasma motilin level. (2) In damaged AP dogs, antroduodenal interdigestive MMC contractions were suppressed; cyclic, phasic and migratory pattern of MMC was disrupted. Plasma motilin concentration was decreased. Intravenous injection of motilin could not induce phase III contractions. CONCLUSIONS: The area postrema might play an important role, which is mediated by motilin, on the regulation of interdigestive MMC.