Effects of a novel guanylate cyclase inhibitor on nitric oxide-dependent inhibitory neurotransmission in canine proximal colon
Effects of a novel guanylate cyclase inhibitor on nitric oxide-dependent inhibitory neurotransmission in canine proximal colon
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DOI：
10.1038/sj.bjp.0701487
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发表时间：
1997-11-01
影响因子：
7.3
通讯作者：
Shuttleworth, CWR
中科院分区：
文献类型：
--
作者：
Franck, H;Sweeney, KM;Shuttleworth, CWR
1以往的研究表明，一氧化氮（NO）可能通过cGMP依赖和非cGMP依赖两种机制引起犬结肠平滑肌的超极化和舒张。使用1H-[1，2，4]恶二唑并[4，3-a]喹喔啉-I-酮（ODQ）（一种NO刺激鸟苷酸环化酶的新型抑制剂）对这一假设进行了测试。2在组胺（30 μ M）、阿托品和吲哚美辛（均为1 μ M）存在的情况下，内源性神经元的电场刺激（EFS; 5 Hz）可抑制由NO合成引起的阶段性收缩活动。ODQ引起了这种反应的浓度依赖性阻断（10 nM至10 μ M）。3使用细胞内微电极，从位于环形肌层肌间边界附近的肌细胞记录了由于NO合成引起的抑制性连接电位（IJPs）。IJPs被ODQ（1-10 μ M）消除。4 EFS（10-20 Hz）产生频率依赖性抑制电慢波记录从细胞位于粘膜下表面附近的环形肌肉层。这种抑制是由于NO的合成，它被ODQ（1-10 μ M）消除。5由NO供体硝普钠产生的超极化和弛豫被ODQ预处理（1-10 μ M）消除。相反，8-Br-cGMP（1 mM）的抑制反应不受ODQ的影响。6 ODQ单独（1-10 μ M）对自发电或阶段性收缩活动没有显着影响。在用L-NAME（300 μ M）预处理的组织中，ODQ降低了自发或组胺刺激的阶段性收缩活动的幅度。7这些结果表明，犬结肠内源性释放和外源性应用NO的电和机械效应主要是由于ODQ敏感的可溶性鸟苷酸环化酶合成cGMP。没有证据支持NO作用的直接（cGMP-非依赖性）机制，ODQ似乎也引起肌肉收缩活动的非特异性抑制，然而，这种作用并不有助于阻断NO依赖性作用。
1 Previous studies suggested that nitric oxide (NO) may cause hyperpolarization and relaxation of canine colonic smooth muscle by both cGMP-dependent and cGMP-independent mechanisms. This hypothesis was tested using 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-I-one (ODQ), a novel inhibitor of NO-stimulated guanylate cyclase.2 In the presence of histamine (30 mu M), atropine and indomethacin (both at 1 mu M), electrical field stimulation of intrinsic neurons (EFS; 5 Hz) produced inhibition of phasic contractile activity that is due to NO synthesis. ODQ caused a concentration-dependent block of this response (10 nM to 10 mu M).3 Inhibitory junction potentials (IJPs) due to NO synthesis were recorded from muscle cells located near the myenteric border of the circular muscle layer, using intracellular microelectrodes. IJPs were abolished by ODQ (1-10 mu M).4 EFS (10-20 Hz) produced frequency-dependent inhibition of electrical slow waves recorded from cells located near the submucosal surface of the circular muscle layer. This inhibition is due to NO synthesis, and it was abolished by ODQ (1-10 mu M).5 Hyperpolarization and relaxation produced by an NO donor, sodium nitroprusside, were abolished by ODQ pretreatment (1-10 mu M). In contrast, inhibitory responses to 8-Br-cGMP (1 mM) were unaffected by ODQ.6 ODQ alone (1-10 mu M) had no significant effect on spontaneous electrical or phasic contractile activity. In tissues pre-treated with L-NAME (300 mu M), ODQ decreased the amplitude of spontaneous or histamine-stimulated phasic contractile activity.7 These results suggest that electrical and mechanical effects of endogenously released and exogenously applied NO in canine colon are largely due to cGMP synthesis by ODQ-sensitive soluble guanylate cyclase. No evidence to support a direct (cGMP-independent) mechanism of NO action was found. ODQ also appears to cause a non-specific inhibition of muscle contractile activity; however, this effect does not contribute to block of NO-dependent effects.