Knoll J
Eur J Pharmacol. 1976 Oct;39(2):403-7. doi: 10.1016/0014-2999(76)90152-7.
Methionine-enkephalin methylester (MEM) and leucine-enkephalin (LE) inhabit the vasoconstrictor responses of the rabbit ear artery to nerve stimulation by acting on a specific neuronal peptide (enkephalin)-receptor insensitive to opiate agonists. The tetrapeptide: H-Tyr-Gly-Phe-Leu-OCH3 is ineffective. This is the first instance of enkephalins acting in an organ devoid of receptors. In a new test for the analysis of opiate receptors, MEM (ID50=6.9 X 10(-9) M) was a potent inhibitor of transmission. The presence was shown of opiate receptors in the brain which were insensitive to high i.v. or intraventricular doses of enkephalins. It is concluded that enkephalins are not natural ligands to the opiate receptors, but that some of the receptors confuse these structures because of similar characteristics which determine the binding of both opiates and peptides.
甲硫氨酸脑啡肽甲酯（MEM）和亮氨酸脑啡肽（LE）通过作用于对阿片类激动剂不敏感的特定神经元肽（脑啡肽）受体，抑制兔耳动脉对神经刺激的血管收缩反应。四肽：H-Tyr-Gly-Phe-Leu-OCH3无效。这是脑啡肽在缺乏受体的器官中发挥作用的首个实例。在一项用于分析阿片受体的新测试中，MEM（半数抑制浓度=6.9×10⁻⁹ M）是一种强效的传递抑制剂。研究表明，脑内存在对高静脉注射或脑室内注射剂量的脑啡肽不敏感的阿片受体。得出的结论是，脑啡肽不是阿片受体的天然配体，但由于决定阿片类药物和肽类结合的相似特性，一些受体将这些结构混淆。
