Muscarinic Signaling Pathways Affecting Cardiac Channels

描述（由申请人提供）：副交感神经刺激产生 对心率和收缩力的显著影响，通过释放 神经递质乙酰胆碱，然后激活毒蕈碱受体 在所有心肌细胞上都有这些影响全部或部分地通过 通过影响心脏离子通道的直接和间接信号机制 活动间接作用涉及调节cAMP依赖的 β-肾上腺素能反应事实上，毒蕈碱受体激活抑制了 以及促进β-肾上腺素能反应，表明净结果 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 作用仅由一氧化氮（NO）的产生介导。然而，在这方面， 这种信号传导机制在介导毒蕈碱 成年人心室肌细胞的反应。我们的假设是 是发育调节的信号通路耦合毒蕈碱 受体调节β-肾上腺素能反应，这可能导致细胞 在成人心脏中的类型特异性信号传导机制。如果是这样， 那么是什么导致了成人心室肌的毒蕈碱反应呢 肌细胞？有无可争议的证据表明，抑制作用可以 通过腺苷酸环化酶V型的直接G依赖性抑制和/或 VI（AC 5和AC 6）。然而，我们提出了一个新的想法， 这种效应是由于AC 4和/或AC 7的直接G依赖性刺激。因此 本提案的具体目的是检验以下四个假设： 1)NO不参与毒蕈碱抑制或毒蕈碱抑制 成年心室肌细胞的刺激反应; 2）毒蕈碱刺激 成人心室肌细胞的反应是由于直接G蛋白依赖 特异性AC亚型的活化; 3）NO确实有助于毒蕈碱 心房肌细胞中的抑制性和muscannic刺激性信号传导机制; NO也参与新生儿心肌细胞M信号转导机制 心室肌细胞我们将使用控制和基因改变的动物模型 确定参与介导毒蕈碱反应的信号通路， 通过记录CAMP调节的心脏离子通道活性， 在分离的心肌细胞中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.