Gallego Diana, Gil Víctor, Aleu Jordi, Aulí Mariona, Clavé Pere, Jiménez Marcel
Department of Cell Biology, Physiology and Immunology, Edifici V, Universitat Autònoma de Barcelona 08193, Bellaterra, Barcelona, Spain.
Am J Physiol Gastrointest Liver Physiol. 2008 Sep;295(3):G522-33. doi: 10.1152/ajpgi.00510.2007. Epub 2008 Jul 3.
The aim of the present work is to investigate a putative junction transmission [nitric oxide (NO) and ATP] in the human colon and to characterize the electrophysiological and mechanical responses that might explain different functions from both neurotransmitters. Muscle bath and microelectrode techniques were performed on human colonic circular muscle strips. The NO donor sodium nitroprusside (10 microM), but not the P2Y receptor agonist adenosine 5'-O-2-thiodiphosphate (10 microM), was able to cause a sustained relaxation. NG-nitro-L-arginine (L-NNA) (1 mM), a NO synthase inhibitor, but not 2'-deoxy-N6-methyl adenosine 3',5'-diphosphate tetraammonium salt (MRS 2179) (10 microM), a P2Y antagonist, increased spontaneous motility. Electrical field stimulation (EFS) at 1 Hz caused fast inhibitory junction potentials (fIJPs) and a relaxation sensitive to MRS 2179 (10 microM). EFS at higher frequencies (5 Hz) showed biphasic IJP with fast hyperpolarization sensitive to MRS 2179 followed by sustained hyperpolarization sensitive to L-NNA; both drugs were needed to fully block the EFS relaxation at 2 and 5 Hz. Two consecutive single pulses induced MRS 2179-sensitive fIJPs that showed a rundown. The rundown mechanism was not dependent on the degree of hyperpolarization and was present after incubation with L-NNA (1 mM), hexamethonium (100 microM), MRS 2179 (1 microM), and NF023 (10 microM). We concluded that single pulses elicit ATP release from enteric motor neurons that cause a fIJP and a transient relaxation that is difficult to maintain over time; also, NO is released at higher frequencies causing a sustained hyperpolarization and relaxation. These differences might be responsible for complementary mechanisms of relaxation being phasic (ATP) and tonic (NO).
本研究的目的是探究人结肠中一种假定的接头传递（一氧化氮和三磷酸腺苷），并描述可能解释这两种神经递质不同功能的电生理和机械反应。对人结肠环形肌条进行了肌肉浴和微电极技术实验。一氧化氮供体硝普钠（10微摩尔）能够引起持续舒张，而P2Y受体激动剂5'-O-2-硫代二磷酸腺苷（10微摩尔）则不能。一氧化氮合酶抑制剂N-硝基-L-精氨酸（L-NNA）（1毫摩尔）可增加自发运动性，而P2Y拮抗剂2'-脱氧-N6-甲基腺苷3',5'-二磷酸四铵盐（MRS 2179）（10微摩尔）则无此作用。1赫兹的电场刺激（EFS）可引起快速抑制性接头电位（fIJPs）和对MRS 2179（10微摩尔）敏感的舒张。更高频率（5赫兹）的EFS显示双相抑制性接头电位，快速超极化对MRS 2179敏感，随后是对L-NNA敏感的持续超极化；在2赫兹和5赫兹时，两种药物都需要才能完全阻断EFS诱导的舒张。两个连续的单脉冲可诱导对MRS 2179敏感的fIJPs，且这些电位会出现衰减。衰减机制不依赖于超极化程度，在与L-NNA（1毫摩尔）、六甲铵（100微摩尔）、MRS 2179（1微摩尔）和NF023（10微摩尔）孵育后仍然存在。我们得出结论，单脉冲可促使肠运动神经元释放三磷酸腺苷，导致fIJP和难以长时间维持的短暂舒张；此外，在更高频率时释放一氧化氮，引起持续超极化和舒张。这些差异可能是导致舒张的互补机制呈现阶段性（三磷酸腺苷）和持续性（一氧化氮）的原因。
