Kitazawa T, Taneike T, Ohga A
Department of Veterinary Pharmacology, Faculty of Dairy Science, Rakuno Gakuen University, Ebetsu, Japan.
Peptides. 1995;16(7):1243-52. doi: 10.1016/0196-9781(95)00095-2.
The effects of a porcine motilin analogue, [Leu13]motilin (LMT) on the smooth muscle preparations isolated from the chicken gastrointestinal (GI) tract were investigated in vitro. In the proventriculus, LMT (100 nM to 30 microM) caused an atropine-sensitive contraction and enhanced the electrical field stimulation (EFS)- or 1,1-dimethyl-4-phenyl-piperazinium (DMPP)-induced contraction without affecting the response to acetylcholine (ACh). LMT also caused a concentration-dependent contraction of the intestinal tract (duodenum, jejunum, ileum, and colon). The responsiveness to LMT was strongest in the jejunum and weakest in the colon. The responses to LMT in the intestinal segments were not affected by tetrodotoxin, atropine, hexamethonium, pyrilamine, spantide, and 5-hydroxyltryptamine-induced desensitzation, but significantly decreased by verapamil or removal of external Ca2+. LMT did not enhance the EFS- or DMPP-induced contraction in the ileum. Canine motilin also contracted the intestinal segments in a similar concentration range to LMT with an equal potency, but erythromycin A (EMA) and N-ethyl-N-demethyl-8,9-anhydroerythromycin A, 6-9-hemiketal (EM523) showed only a weak contractile activity even at high concentration (up to 100 microM), indicating that motilin receptors in the chicken intestine were somewhat different from those of mammals. In conclusion, LMT produces an excitatory response in the chicken GI tract with a different sensitivity from region to region. The mechanisms of the action were different between the proventriculus and small intestine; that is, LMT contracts the small intestine through the direct action on the smooth muscle cells, but this peptide acts on the enteric cholinergic neurones and stimulates ACh release, and thus regulates autonomic neuroeffector transmission in the proventriculus.
在体外研究了猪胃动素类似物[Leu13]胃动素（LMT）对从鸡胃肠道（GI）分离的平滑肌制剂的作用。在前胃中，LMT（100 nM至30 microM）引起阿托品敏感的收缩，并增强电场刺激（EFS）或1,1 - 二甲基 - 4 - 苯基 - 哌嗪鎓（DMPP）诱导的收缩，而不影响对乙酰胆碱（ACh）的反应。LMT还引起肠道（十二指肠、空肠、回肠和结肠）的浓度依赖性收缩。对LMT的反应在空肠中最强，在结肠中最弱。肠道段对LMT的反应不受河豚毒素、阿托品、六甲铵啶、吡苄明、spantide和5 - 羟色胺诱导的脱敏影响，但维拉帕米或去除细胞外Ca2 +可使其显著降低。LMT在回肠中不增强EFS或DMPP诱导的收缩。犬胃动素也在与LMT相似的浓度范围内以相同效力使肠道段收缩，但红霉素A（EMA）和N - 乙基 - N - 去甲基 - 8,9 - 脱水红霉素A，6 - 9 - 半缩酮（EM523）即使在高浓度（高达100 microM）时也仅表现出微弱的收缩活性，表明鸡肠道中的胃动素受体与哺乳动物的有所不同。总之，LMT在鸡胃肠道中产生兴奋性反应，不同区域的敏感性不同。前胃和小肠的作用机制不同；也就是说，LMT通过直接作用于平滑肌细胞使小肠收缩，但该肽作用于肠胆碱能神经元并刺激ACh释放，从而调节前胃中的自主神经效应传递。
