Radomirov R, Venkova K, Davidoff M, Pencheva N
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Peptides. 1990 May-Jun;11(3):417-25. doi: 10.1016/0196-9781(90)90037-6.
Naloxone-dependent effects of Met-enkephalin (10(-8) M) on the spontaneous and electrically induced mechanical activities were studied in longitudinal and circular preparations isolated from the cat duodenum, jejunum and ileum. Met-Enkephalin changed the spontaneous activity of all preparations tested with the exception of the circular preparations from the ileum. Met-Enkephalin-induced responses of the longitudinal preparations from the ileum were abolished by treatment with tetrodotoxin (10(-7) M), while the responses of both longitudinal and circular preparations from the duodenum and jejunum were only partially depressed, being resistant to tetrodotoxin components. The latter were most pronounced in the duodenum. The neurogenic electrically induced (0.5 msec, 5 Hz, 150 pulses) responses of all the preparations consisted mainly of contractile components which were significantly and naloxone-dependently reduced by Met-enkephalin (10(-8) M). The contractile components of the responses, which were reduced by Met-enkephalin, were entirely abolished by atropine (3 x 10(-6) M). Both Met-enkephalin and atropine inhibitory effects on the neurogenic responses were more pronounced in the ileum. Met-Enkephalin was found in nerve fibers of the myenteric plexus distributed mainly among the circular muscle. Single immunoreactive nerve fibers were observed in the longitudinal muscle layer of the duodenum but not in the jejunum and ileum. The distribution of Met-enkephalin-like immunoreactivity along the small intestine did not show significant differences among the three intestinal regions tested. The results obtained suggest that Met-enkephalin can modulate the mechanical activity of the cat small intestine, inhibiting cholinergic transmission and/or activating smooth muscle opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
在从猫十二指肠、空肠和回肠分离出的纵向和环形标本中，研究了甲硫氨酸脑啡肽（10⁻⁸M）对自发和电诱导机械活动的纳洛酮依赖性作用。甲硫氨酸脑啡肽改变了除回肠环形标本外所有测试标本的自发活动。用河豚毒素（10⁻⁷M）处理可消除甲硫氨酸脑啡肽诱导的回肠纵向标本的反应，而十二指肠和空肠纵向和环形标本的反应仅部分受到抑制，对河豚毒素成分有抗性。后者在十二指肠中最为明显。所有标本的神经源性电诱导（0.5毫秒，5赫兹，150个脉冲）反应主要由收缩成分组成，甲硫氨酸脑啡肽（10⁻⁸M）可显著且纳洛酮依赖性地降低这些成分。被甲硫氨酸脑啡肽降低的反应收缩成分被阿托品（3×10⁻⁶M）完全消除。甲硫氨酸脑啡肽和阿托品对神经源性反应的抑制作用在回肠中更为明显。在主要分布于环形肌之间的肌间神经丛神经纤维中发现了甲硫氨酸脑啡肽。在十二指肠的纵肌层中观察到单条免疫反应性神经纤维，但在空肠和回肠中未观察到。在所测试的三个肠段中，沿小肠的甲硫氨酸脑啡肽样免疫反应性分布未显示出显著差异。所得结果表明，甲硫氨酸脑啡肽可调节猫小肠的机械活动，抑制胆碱能传递和/或激活平滑肌阿片受体。（摘要截短于250字）
