Ivancheva C, Radomirov R
Laboratory of Peripheral Synapses, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Methods Find Exp Clin Pharmacol. 1996 Oct;18(8):521-5.
Met-enkephalin-induced modulation of tetrodotoxin (0.1 microM)-sensitive nonadrenergic, noncholinergic (NANC) nerve-mediated responses of the longitudinal muscle layer of guinea pig ileum during electrical field stimulation (EFS, 0.8 ms, 40 V, 20 s, 1 Hz or 10 Hz) were studied. The response to EFS of untreated preparations was a twitch followed by a low-amplitude tonic contraction. The NANC nerve-mediated response revealed in the presence of phentolamine (5 microM), propranolol (5 microM) and atropine (3 microM) consisted of relaxation followed by a twitch and a tonic contraction. The relaxation was inhibited by NG-nitro-L-arginine (0.1-0.5 mM), a nitric oxide synthase inhibitor. L-arginine (0.5 mM), a substrate of nitric oxide synthase, restored the relaxation to the initial level indicating its nitrergic origin. After adenosine 5'-triphosphate-induced desensitization of purinoceptors the relaxation was enhanced while the contractions decreased. Met-enkephalin (1 nM-1 microM) abolished (J-Hz EFS) or reduced (10-Hz EFS) the relaxation in a frequency-dependent manner, suggesting an inhibitory prejunctional enkephalinergic mechanism modulating the nitrergically mediated relaxant events in the longitudinal muscle layer.
研究了甲硫氨酸脑啡肽对豚鼠回肠纵肌层在电场刺激（EFS，0.8毫秒，40伏，20秒，1赫兹或10赫兹）期间对河豚毒素（0.1微摩尔）敏感的非肾上腺素能、非胆碱能（NANC）神经介导反应的调节作用。未经处理的标本对EFS的反应是一次抽搐，随后是低幅度的强直性收缩。在酚妥拉明（5微摩尔）、普萘洛尔（5微摩尔）和阿托品（3微摩尔）存在下显示的NANC神经介导反应包括松弛，随后是一次抽搐和一次强直性收缩。一氧化氮合酶抑制剂NG-硝基-L-精氨酸（0.1-0.5毫摩尔）可抑制松弛。一氧化氮合酶的底物L-精氨酸（0.5毫摩尔）可使松弛恢复到初始水平，表明其起源于氮能。在三磷酸腺苷诱导嘌呤受体脱敏后，松弛增强而收缩减弱。甲硫氨酸脑啡肽（1纳摩尔-1微摩尔）以频率依赖的方式消除（1赫兹EFS）或减少（10赫兹EFS）松弛，提示存在一种抑制性接头前脑啡肽能机制，调节纵肌层中氮能介导的松弛事件。
