Nitrergic relaxation in the gastrointestinal tract of mice with cell-specific deletion of NO-sensitive guanylyl cyclase

no敏感的鸟苷环化酶（NO-GC）催化细胞内第二信使cGMP的产生。该酶在NO/cGMP信号传导中起关键作用。NO-GC是信号分子一氧化氮最重要的受体，参与多种生理功能的调控。我们已经产生了普遍缺乏NO-GC的小鼠。这些小鼠患有高血压、胃肠运动障碍和过早死亡。负责个体表型的细胞/组织的确切身份仍有待解决。一般GCKO小鼠的胃肠运动减弱可以解释为氮能松弛的丧失。氮能弛豫的确切机制尚未得到彻底的研究。神经释放的NO是直接作用于平滑肌细胞（SMC）的松弛（类似于血管系统内皮NO的作用），还是介入Cajal间质细胞（ICC）介导氮能松弛，目前在该领域的讨论较多。此外，第三种细胞类型称为“成纤维细胞样细胞”，具有高NO-GC表达。我们已经产生了NO-GC在SMC或ICC中被特异性删除的KO小鼠。GI组织的氮能松弛在两个单敲除中受到中度影响。在SMC和ICC中携带NO-GC缺失的双突变体显示出GI运动性的强烈降低和几乎完全缺乏氮能松弛。在本项目中，我们希望生成FLC中缺乏NO-GC的小鼠；此外，我们将产生两倍和三倍突变体。器官浴实验和测量膜电位包括抑制连接电位将进行。在这些小鼠肠道中最重要的NO- gc表达细胞缺乏NO受体的帮助下，我们将研究这些细胞的相互作用，并确定氮能松弛的确切机制。

NO-sensitive guanylyl cyclase (NO-GC) catalyzes the generation of the intracellular second messenger cGMP. The enzyme plays a key role within NO/cGMP signalling. Being the most important receptor for the signal molecule nitric oxide, NO-GC participates in the regulation of many different physiological functions.We have generated mice which lack NO-GC ubiquitously. These mice are hypertensive, suffer from gastrointestinal dysmotility and die prematurely. The exact identity of the cells/tissues responsible for the individual phenotypes remains to be resolved.The reduced GI motility in the general GCKO mice can be explained by the loss of nitrergic relaxation. The exact mechanism of nitrergic relaxation has not been investigated thoroughly. It is currently being heavily discussed in the field whether neuronally released NO acts to relax smooth muscle cells (SMC) directly (similar to the action of endothelial NO in the vascular system) or whether interstitial cells of Cajal (ICC) are interposed to mediate nitrergic relaxation. In addition, a third cell type called 'fibroblast-like cell' with high NO-GC expression has been identified.We have already generated KO mice in which NO-GC is deleted specifically in SMC or in ICC. Nitrergic relaxation of GI tissue is moderately affected in the two single knockouts. A double mutant carrying a deletion of NO-GC in both SMC and ICC shows strong reduction of GI motility and an almost total lack of nitrergic relaxation. In this project, we would like to generate mice that lack NO-GC in FLC; in addition, we will generate double and triple mutants. Organ bath experiments and measurements of membrane potential including inhibitory junction potentials will be performed. With the help of these mice lacking the NO receptor in the most important NO-GC expressing cells in the gut, we will investigate the interplay of these cells and identify the exact mechanism of nitrergic relaxation.