Yang Qing, Sumner Andrew D, Puhl Henry L, Ruiz-Velasco Victor
Department of Anesthesiology, H187, Penn State College of Medicine, 500 University Dr., Hershey, PA 17033-0850, USA.
J Neurophysiol. 2006 Nov;96(5):2479-87. doi: 10.1152/jn.00093.2006. Epub 2006 Sep 27.
Muscarinic acetylcholine receptors (mAChRs) are known to mediate the acetylcholine inhibition of Ca(2+) channels in central and peripheral neurons. Stellate ganglion (SG) neurons provide the main sympathetic input to the heart and contribute to the regulation of heart rate and myocardial contractility. Little information is available regarding mAChR regulation of Ca(2+) channels in SG neurons. The purpose of this study was to identify the mAChR subtypes that modulate Ca(2+) channel currents in rat SG neurons innervating heart muscle. Accordingly, the modulation of Ca(2+) channel currents by the muscarinic cholinergic agonist, oxotremorine-methiodide (Oxo-M), and mAChR blockers was examined. Oxo-M-mediated mAChR stimulation led to inhibition of Ca(2+) currents through voltage-dependent (VD) and voltage-independent (VI) pathways. Pre-exposure of SG neurons to the M(1) receptor blocker, M(1)-toxin, resulted in VD inhibition of Ca(2+) currents after Oxo-M application. On the other hand, VI modulation of Ca(2+) currents was observed after pretreatment of cells with methoctramine (M(2) mAChR blocker). The Oxo-M-mediated inhibition was nearly eliminated in the presence of both M(1) and M(2) mAChR blockers but was unaltered when SG neurons were exposed to the M(4) mAChR toxin, M(4)-toxin. Finally, the results from single-cell RT-PCR and immunofluorescence assays indicated that M(1) and M(2) receptors are expressed and located on the surface of SG neurons. Overall, the results indicate that SG neurons that innervate cardiac muscle express M(1) and M(2) mAChR, and activation of these receptors leads to inhibition of Ca(2+) channel currents through VI and VD pathways, respectively.
已知毒蕈碱型乙酰胆碱受体（mAChRs）介导中枢和外周神经元中乙酰胆碱对Ca(2+)通道的抑制作用。星状神经节（SG）神经元是心脏主要的交感神经输入来源，对心率和心肌收缩力的调节起作用。关于SG神经元中Ca(2+)通道的mAChR调节作用，目前所知甚少。本研究的目的是确定调节支配心肌的大鼠SG神经元中Ca(2+)通道电流的mAChR亚型。因此，研究了毒蕈碱胆碱能激动剂氧化震颤素甲碘化物（Oxo-M）和mAChR阻滞剂对Ca(2+)通道电流的调节作用。Oxo-M介导的mAChR刺激导致通过电压依赖性（VD）和电压非依赖性（VI）途径抑制Ca(2+)电流。将SG神经元预先暴露于M(1)受体阻滞剂M(1)-毒素后，应用Oxo-M会导致Ca(2+)电流的VD抑制。另一方面，在用甲溴东莨菪碱（M(2) mAChR阻滞剂）预处理细胞后，观察到Ca(2+)电流的VI调节。在同时存在M(1)和M(2) mAChR阻滞剂的情况下，Oxo-M介导的抑制作用几乎消除，但当SG神经元暴露于M(4) mAChR毒素M(4)-毒素时，抑制作用未改变。最后，单细胞逆转录聚合酶链反应（RT-PCR）和免疫荧光分析结果表明，M(1)和M(2)受体在SG神经元表面表达并定位。总体而言，结果表明支配心肌的SG神经元表达M(1)和M(2) mAChR，这些受体的激活分别通过VI和VD途径导致Ca(2+)通道电流的抑制。
