Gericke Adrian, Mayer Veronique G A, Steege Andreas, Patzak Andreas, Neumann Ulrike, Grus Franz H, Joachim Stephanie C, Choritz Lars, Wess Jürgen, Pfeiffer Norbert
Department of Ophthalmology, Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Invest Ophthalmol Vis Sci. 2009 Oct;50(10):4822-7. doi: 10.1167/iovs.09-3600. Epub 2009 Apr 30.
To determine the functional role of M(3) and M(5) muscarinic acetylcholine receptor subtypes in ophthalmic arteries using gene-targeted mice.
Muscarinic receptor gene expression was quantified in murine ophthalmic arteries using real-time PCR. To test the functional relevance of M(3) and M(5) receptors, ophthalmic arteries from mice deficient in either subtype (M3R(-/-), M5R(-/-), respectively) and wild-type controls were isolated, cannulated with micropipettes, and pressurized. Changes in luminal vessel diameter in response to muscarinic and nonmuscarinic receptor agonists were measured by video microscopy.
With the use of real-time PCR, all five muscarinic receptor subtypes were detected in ophthalmic arteries. However, mRNA levels of M(1), M(3), and M(5) receptors were higher than those of M(2) and M(4) receptors. In functional studies, after preconstriction with phenylephrine, acetylcholine and carbachol produced concentration-dependent dilations of ophthalmic arteries that were similar in M5R(-/-) and wild-type mice. Strikingly, cholinergic dilation of ophthalmic arteries was almost completely abolished in M3R(-/-) mice. Deletion of either M(3) or M(5) receptor did not affect responses to nonmuscarinic vasodilators such as bradykinin or nitroprusside.
These findings provide the first evidence that M(3) receptors are critically involved in cholinergic regulation of diameter in murine ophthalmic arteries.
利用基因敲除小鼠确定M3和M5毒蕈碱型乙酰胆碱受体亚型在眼动脉中的功能作用。
使用实时聚合酶链反应（PCR）对小鼠眼动脉中的毒蕈碱受体基因表达进行定量。为了测试M3和M5受体的功能相关性，分别从小鼠中缺乏任一亚型（分别为M3R(-/-)、M5R(-/-)）和野生型对照中分离出眼动脉，用微量移液器插管并加压。通过视频显微镜测量毒蕈碱和非毒蕈碱受体激动剂引起的管腔血管直径变化。
使用实时PCR，在眼动脉中检测到所有五种毒蕈碱受体亚型。然而，M1、M3和M5受体的mRNA水平高于M2和M4受体。在功能研究中，用去氧肾上腺素预收缩后，乙酰胆碱和卡巴胆碱使眼动脉产生浓度依赖性扩张，在M5R(-/-)和野生型小鼠中相似。令人惊讶的是，M3R(-/-)小鼠中眼动脉的胆碱能扩张几乎完全消失。缺失M3或M5受体均不影响对非毒蕈碱血管舒张剂如缓激肽或硝普钠的反应。
这些发现提供了首个证据，即M3受体在小鼠眼动脉直径的胆碱能调节中起关键作用。
