目的：研究一氧化氮（ NO）对豚鼠左心室流出道自发电活动的影响及其对缺血／再灌注（ I／R）时自发电活动改变的影响。方法：采用标准玻璃微电极细胞内电位记录技术观测外源性NO供体硝普钠（ SNP）对豚鼠左心室流出道自发慢反应电位的影响及其对I／R时该电位改变的影响。结果：1、10、100μmol／L SNP呈浓度依赖性地导致4相自动除极速度（ VDD）和自发放电频率（ RPF）明显增加，但1000μmol／L SNP的效应不明显。 SNP呈浓度依赖性地导致最大舒张电位（ MDP）绝对值和动作电位幅度（ APA）增大，0相最大除极速度（ Vmax ）加快，复极50％和90％时间（APD50和APD90）缩短。缺血10 min组VDD和RPF明显减慢，APA和Vmax明显增大，APD50和APD90明显延长。与缺血10 min组相比，再灌注10 min组VDD和RPF明显加快，且常出现节律不齐，MDP绝对值和APA明显减小，APD50和APD90明显缩短。1、10、100μmol／L SNP再灌注时可明显改善缺血造成的VDD和RPF减慢以及再灌注造成的节律不齐，1000μmol／L SNP的上述效应不明显。各浓度SNP再灌注时均可使缺血造成的APA和APD的改变恢复至对照组水平。结论：SNP可呈浓度依赖性地增加左心室流出道的自律性，并可明显改善I／R导致的自发慢反应电位的改变。%AIM: To study the electrophysiological effects of nitric oxide (NO) on the pacemaker cells in guinea-pig left ventricular outflow tract under the condition of ischemia/reperfusion ( I/R) .METHODS:The spontaneous slow action potentials of guinea-pig left ventricular outflow tract were recorded by conventional intracellular microelectrode technique.The effects of NO donor sodium nitroprusside ( SNP) on the spontaneous slow action potentials under normal or I/R condition were investigated.RESULTS:SNP at concentrations of 1, 10 and 100μmol/L but not 1000μmol/L signif-icantly increased velocity of diastolic depolarization ( VDD) and rate of pacemaker firing ( RPF) , SNP at concentrations of 1, 10, 100 and 1 000μmol/L notably increased maximal diastolic potential (MDP), amplitude of action potential (APA) and maximal rate of depolarization ( Vmax ) , shortened 50%and 90%of the duration ( APD50 and APD90 ) .In ischemia 10 min group, VDD and RPF were significantly decreased, APA and Vmax were notably increased, and APD50 and APD90 were markedly lengthened compared with control group.In reperfusion 10 min group, VDD and RPF were significantly in-creased, MDP and APA were notably decreased, and APD50 and APD90 were markedly shortened compared with I 10 min group.In reperfusin 10 min group, the pacemaker activity was always irregular.In reperfusion 10 min group, the parame-ters of spontaneous slow action potentials restored to the levels of control group except for VDD and Vmax .In 1, 10 and 100 μmol/L SNP+R groups, VDD and RPF were significantly increased than in ischemia 10 min group .In 1, 10, 100 and 1 000 μmol/L SNP+R groups, APA, APD50 and APD90 were restored to the levels of control group.CONCLUSION:SNP significantly increases the spontaneous activity of left ventricular outflow tract, and relieves the effects of I/R on the sponta-neous slow action potential markedly.
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