Radomirov R, Pencheva N, Venkova K, Davidoff M
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Neuropeptides. 1990 Sep;17(1):35-44. doi: 10.1016/0143-4179(90)90139-p.
In longitudinal and circular strips from cat terminal ileum field electrical stimulation at a frequency of 2 Hz evoked contractile responses. Stimulation at frequencies of 10 or 30 Hz elicited contractions of the longitudinal muscle and relaxations of the circular strips. (Met-5) enkephalin (1 nM) naloxone-dependently reduced the contractile and increased the inhibitory responses. Atropine (3 microM) converted the contractile responses to slight relaxations and potentiated the inhibitory responses. After atropine (3 microM) and guanethidine (50 microM) both longitudinal and circular strips responded to electrical stimulation with relaxations. In atropine-pretreated strips (Met-5) enkephalin was effective only in the circular strips, increasing the inhibitory responses. In contrast, after atropine and guanethidine (Met-5) enkephalin decreased these inhibitory responses. In unstimulated strips (Met-5) enkephalin failed to change the responses to acetylcholine and noradrenaline. It is concluded that (Met-5) enkephalin reduces the excitatory cholinergic components of the electrically-evoked responses in both longitudinal and circular strips as well as the excitatory adrenergic and the inhibitory non-adrenergic, non-cholinergic components of the responses in the circular strips by acting presynaptically. Demonstration of (Met-5) enkephalin-like immunoreactivity showed immunostaining in nerves of the myenteric plexus and in nerve fibers between the smooth muscle cells suggesting that (Met-5) enkephalin effects could be also of physiological significance.
在猫末端回肠的纵向和环形肌条上，以2 Hz的频率进行场电刺激可诱发收缩反应。以10或30 Hz的频率刺激可引起纵向肌收缩和环形肌条舒张。（蛋氨酸-5）脑啡肽（1 nM）可纳洛酮依赖性地降低收缩反应并增强抑制反应。阿托品（3 microM）可将收缩反应转变为轻微舒张，并增强抑制反应。在阿托品（3 microM）和胍乙啶（50 microM）处理后，纵向和环形肌条对电刺激均表现为舒张反应。在经阿托品预处理的肌条中，（蛋氨酸-5）脑啡肽仅对环形肌条有效，可增强抑制反应。相反，在阿托品和胍乙啶处理后，（蛋氨酸-5）脑啡肽可降低这些抑制反应。在未受刺激的肌条中，（蛋氨酸-5）脑啡肽未能改变对乙酰胆碱和去甲肾上腺素的反应。结论是，（蛋氨酸-5）脑啡肽通过突触前作用降低纵向和环形肌条电诱发反应中的兴奋性胆碱能成分，以及环形肌条反应中的兴奋性肾上腺素能和抑制性非肾上腺素能、非胆碱能成分。（蛋氨酸-5）脑啡肽样免疫反应性的显示表明，在肌间神经丛的神经和平滑肌细胞之间的神经纤维中有免疫染色，提示（蛋氨酸-5）脑啡肽的作用也可能具有生理意义。
