胆红素干预颈交感神经节乙酰胆碱受体介导阻黄血管低反应性

Vascular hyporeactivity is the main cause of high incidence of peri-operative complications and mortality for patients with obstructive jaundice, and the possible cause including vascular mechanism and peripheral sympathetic nervous mechanism. On the basis of our previous results on vascular mechanism, we will investigate the peripheral sympathetic nervous mechanism for vascular hyporeactivity in obstructive jaundice. Superior cervical ganglion (SCG) takes part in the regulation of cardiovascular function and the neuronal nicotinic acetylcholine receptors (nAChRs) play a key role in ganglionic information processing and transmission, which in turn modulate the catecholamine secretion from ganglion cells. Therefore, we suppose that the obstructive jaundice may affect sympathetic ganglion function and lead to hyporeactivity of the blood vesscle dominated by sympathetic neuron. In the present study, we first investigate the response of patients with obstructive jaundice to vasoactive agents; second, study the effect of obstructive jaundice on the cardiovascular function before and after the vagus nerve transection, and on the protein and mRNA expression of nAChRs in the SCG; third, investigate the effect of obstructive jaundice bilirubin on nAChRs channel current and the effect of bilirubin on the recombined huamn nAChRs channel current by whole-cell patch clamp technique; last, measure the catecholamine secretion of SCG with carbon fiber electrode. We hope to illustrate the peripheral sympathetic nervous mechanism for hyporeactivity of obstructive jaundiced blood vessels, in order to prevent and treat hemodynamic instability in obstructive jaundice patients and decrease the incidence of peri-operative complications and mortality.

梗阻性黄疸（OJ）患者血管低反应是围术期并发症和死亡的主要原因，目前认为包括血管机制和外周交感神经机制。课题组在血管机制研究的基础上，拟进一步研究外周交感神经机制。颈上交感神经节（SCG）参与心血管功能调节，其上的乙酰胆碱受体（nAChRs）负责神经节信息处理和传递，并调节儿茶酚胺类物质的释放。我们推测OJ影响交感神经节的功能，从而导致血管低反应性。本课题首先研究OJ患者对血管活性药物的反应；其次研究OJ对大鼠迷走神经离断前后心血管功能以及急性分离SCG上nAChRs蛋白和mRNA表达的影响；然后以全细胞膜片钳技术检测OJ对大鼠SCG上nAChRs通道电流的影响和胆红素孵育对重组人nAChRs通道电流的影响，最后以微碳纤电极检测OJ和胆红素孵育对SCG胞膜儿茶酚胺类物质分泌的影响。我们希望能阐明OJ患者血管低反应性的外周交感神经机制，防治围术期血流动力学紊乱，降低并发症的发生率和死亡率。

目的：.研究胆红素，以及胆红素复合七氟烷对正常大鼠急性分离的颈上交感神经节细胞（SCG）乙酰胆碱受体（nAChRs）通道电流的影响，以探讨梗阻性黄疸时血管低反应的机制。.方法：.酶消化法急性分离SD大鼠（5-7d）颈上交感神经节细胞，全细胞膜片钳技术记录胆红素、胆红素复合七氟烷对其nAChRs通道电流的影响。.结果：胆红素对ACh诱发电流峰值的影响呈双向性，低浓度胆红素（0.5和2mM）增加ACh诱发电流的峰值，而高浓度胆红素（3和5.52mM）则抑制Ach诱发的电流；同时胆红素浓度依赖性降低乙酰胆碱受体的脱敏幅度。胆红素对乙酰胆碱受体通道电流的抑制为非竞争性、非电压依赖性抑制。.给予100 μM Ach可诱发出迅速激活的nAchR电流，当给予复合胆红素后，胆红素显著增加了七氟烷对nAchR通道电流的抑制程度，且胆红素在一定程度上降低了低浓度七氟烷对nAchR通道电流的5s脱敏感率。.IC50浓度的胆红素可降低低浓度七氟烷对nAChR通道电流的抑制作用；当七氟烷的浓度达486 μM时，胆红素对七氟烷抑制nAChRs通道电流的作用影响较小。胆红素降低了七氟烷对nAChRs通道的半数抑制剂量。.胆红素能增加七氟烷对nAchR的抑制作用。胆红素对七氟烷抑制nAChRs通道功能有双重作用，即抑制电流波幅和降低脱敏感衰减率；胆红素主要通过降低通道脱敏感衰减率来减轻低浓度七氟烷对nAChRs通道的抑制作用，而高浓度七氟烷仍以抑制通道电流波幅为主。.结论：.推测梗阻性黄疸时血管低反应性，可能与胆红素抑制神经节后乙酰胆碱受体和负向调控交感神经节传递有关。当合并七氟烷时，胆红素能增加吸入麻醉药对nAchR的抑制作用，有可能加重血管低反应性。