Muscarinic Signaling Pathways Affecting Cardiac Channels

描述(申请人提供)：施加副交感神经刺激 对心率和收缩能力的显著影响 神经递质乙酰胆碱，然后激活毒鼠碱受体 在所有心肌细胞上都有发现。这些影响是全部或部分中介的。 影响心脏离子通道的直接和间接信号机制 活动。间接影响包括对cAMP依赖的调节 β-肾上腺素能反应。事实上，M受体的激活抑制AS 以及促进β-肾上腺素能反应，这表明最终结果是 是这些抑制和刺激作用之间的平衡。最近的证据 提示在心房准备中，抑制性和刺激性 其影响完全通过一氧化氮(NO)的产生来实现。然而， 这一信号机制可能不是那么重要的介导性毒鼠强 成人心室肌细胞的反应。我们的工作假设是 是毒鼠碱偶联信号通路的发育调节吗 调节β-肾上腺素能反应的受体，这可能导致细胞 成人心脏中特定的信号机制。如果是这样的话， 那么是什么导致了成人脑室的毒鼠碱反应呢？ 肌细胞？有毋庸置疑的证据表明，抑制作用可能是 解释为直接依赖于G抑制V型和/或腺苷环化酶 VI(AC5和AC6)。然而，我们提出了一个新的想法，即刺激性 这些效应是由于对AC4和/或AC7的直接G依赖刺激。因此 这项提议的具体目的是检验以下四个假设： 1)NO对毒鼠强的抑制或毒鼠强的作用都没有贡献 成人心肌细胞的刺激性反应；2)毒鼠强刺激性 成人心肌细胞的反应是直接依赖G蛋白的结果 激活特定的AC异构体；3)NO确实有助于毒扁豆碱 心房肌细胞的抑制和肌肉刺激信号机制； 4)NO也参与了新生鼠M胆碱信号转导机制 心室肌细胞。我们将使用对照和转基因动物模型 确定参与介导毒鼠强反应的信号通路 通过记录cAMP调节的心脏离子通道活动 分离的心肌细胞cAMP活性的直接荧光测量。

DESCRIPTION (provided by applicant):Parasympathetic stimulation exerts significant influence on heart rate and contractility through the release of the neurotransmitter acetylcholine, which then activates muscarinic receptors found on all cardiac myocytes. These effects are mediated in whole or in part by direct and indirect signaling mechanisms affecting cardiac ion channel activity. The indirect effects involve modulation of cAMP-dependent beta-adrenergic responses. In fact, muscarinic receptor activation inhibits as well as facilitates beta-adrenergic responses, suggesting that the net result is a balance between these inhibitory and stimulatory effects. Recent evidence suggests that in atrial preparations, both the inhibitory and stimulatory effects are mediated solely by the production of nitric oxide (NO). However, this signaling mechanism may not be as important in mediating muscarinic responses in adult ventricular myocytes. Our working hypothesis is that there is developmental regulation of the signaling pathway coupling muscarinic receptors to modulation of beta-adrenergic responses, which may lead to cell type specific signaling mechanisms in the adult heart. If this is the case, then what is responsible for muscarinic responses in adult ventricular myocytes? There is uncontested evidence that the inhibitory effects can be explained by direct G-dependent inhibition of adenylyl cyclase types V and/or VI (AC5 and AC6). However, we propose the novel idea that the stimulatory effects are due to direct G-dependent stimulation of AC4 and/or AC7. Therefore the specific aims of this proposal are to test the following four hypotheses: 1) NO does not contribute to either muscannic inhibitory or muscarinic stimulatory responses in adult ventricular myocytes; 2) muscarinic stimulatory responses in adult ventricular myocytes are due to direct G protein dependent activation of specific AC isoforms; 3) NO does contribute to muscarinic inhibitory and muscannic stimulatory signaling mechanisms in atrial myocytes; and 4) NO is also involved in muscarinic signaling mechanisms in neonatal ventricular myocytes. We will use control and genetically altered animal models to identify the signaling pathways involved in mediating muscarinic responses by recording CAMP regulated cardiac ion channel activity in conjunction with direct fluorescence measurements of cAMP activity in isolated cardiac myocytes.