5-羟色胺和胃动素在狗小肠移行性复合运动调控中的作用

REGULATORY ROLE OF 5-HYDROXYTRYPTAMINE AND MOTILIN IN MIGRATING MOTOR COMPLEX OF SMALL BOWEL IN DOGS

应用慢性植入小肠腔外应力传感器记录清醒狗小肠移行性复合运动（MMC）。在颈外静脉和支配10－15cm肠段的空肠动脉内分别放置一硅胶管以备灌流药物和取血样品用。本研究观察了静脉和动脉注射药物对小肠MMC的影响及MMC不同时相血浆5-羟色胺（5－HT）和胃动素的浓度变化。结果表明：（1）MMC不同时相血浆5-HT和胃动素浓度呈周期性变化，5-HT峰值在胃动素峰值之前出现。血浆5-HT浓度在MMCⅡ相后期达高峰（41．2±1．3）ng／ml，明显高于MMCI相（22．4±1．1）ng／ml（P＜0．01）；而血浆胃动素浓度在MMCⅢ相时达峰值（580.0±30．2）pg／ml，明显高于MMCI相时的水平（140．0±21．0）pg／ml（P＜0．01）。（2）静脉注射胃动素和空肠肠段动脉局部注射5-HT、胃动素分别引起近端小肠和空肠肠段MMCⅢ相收缩。胃动素在空肠肠段引发的收缩振幅高于5－HT。（3）空肠肠段动脉局部灌流5－HT受体拮抗剂、抗胃动素血清、5，6-双羟色胺和河豚毒素（TTX）均可阻断MMCⅢ相在灌流肠段出现和向远端传播。结论：血浆5-HT和胃动素可能是狗小肠MMC的主要启动因素，5-HT释放高峰先于胃动素峰在MMCⅢ相前出现。肠神经系统的5-HT神经元和胃动素神经元在狗小肠MMC调控中起重要作用。

Migrating motor complex (MMC) was recorded by chronically implanted strain gauge transducers on the serosa of small bowel in conscious dogs. Two silastic catheters for injecting ho and taking blood samples were put respectively in a vena jugularis externa and in a jejunal artery which perfused a 10 ~ 15 cm intestinal segment. The present study was undertaken to observe the effect of drugs administered intravenously and intraarterially on MMC and alterations of plasma 5-hydroxytryptamine(5-HT) and motilin in different phases of MMC. The results showed: (1) Levels of plasma 5-HT and motilin showed cyclical fluctuations in different phases of MMC, and 5-HT reached peak before peak of motilin. Plasma 5-HT level reached a peak [(41.2±1 .3) ng/ml] in the later pened of phase Ⅱ, which increased significantly as compared with phase Ⅰ [ (22.4±1.1 )ng/ml (P < 0.01 ), but plasma motilin level had a peak [ (580.0 ± 30.2) pg/ml]in phaseⅢ of MMC, which was higher than that in phase 1 [ (140.0±21 .0) pg/ml](P < 0.01 ). (2) Intravenous motilin and intraarterial 5-HT and motilin could induce phaseⅢ contraction in the canine proximal small bowel and in the perfused segment respectively. Amplitude of contractions caused by motilin was higher than that by 5-HT in the perfused segment. (3) 5-HT receptor antagonist, motilin antiserum, 5,6-dihydroxytryptamine and tetrodotoxin perfused intra-arterially inhibited erpression of MMC in the perfused segment and its caudal propagation. We conclude that plasma 5-HT and motilin may be dominant factors which initiate MMC of canine small bowel, and 5-HT peak appears before peak of motilin. 5-HT neurons and motilin neurons in enteric nervous system may play an important role in controlling MMC of crane small bowel.