中文摘要：

背景：电生理改变是老化心脏表现的主要特征之一。目的：构建老龄房颤犬模型，观察静脉肌袖细胞动作电位和起搏电流的特征。设计、时间及地点：分组对照动物实验，于2005—03／2007—12在解放军总医院实验动物中心和老年心血管病研究所完成。材料：7-9岁健康杂种老龄犬12只，体质量15～20旭，雌雄兼有。台氏液成分（mmol／L）：NaCl135，KCl5．4，CaCl21．8，MgCl21，NaH2PO40．33，HEPES10，葡萄糖10，pH用NaOH调至7．4。方法：取老龄犬6只，快速起搏8周制备房颤模型，余6只犬未经快速起搏处理作对照。分离静脉肌袖细胞，利用全细胞膜片钳在电流钳模式下记录动作电位，在电压钳模式下记录起搏电流。主要观察指标：老龄犬肺静脉肌袖细胞动作电位的特征、起搏电流、起搏电流的Ⅰ-Ⅴ曲线及起搏电流稳态激活的特征。结果：约82．6％的老龄犬静脉肌袖细胞记录到自动除极和自发性动作电位，而未经快速起搏处理犬的细胞约有40％记录到工作心肌动作电位特征。在-120mv时，房颤模型细胞起搏电流的电流密度为（-2．664-0，4）pA／pF，而对照组细胞的电流密度为（-1．24±0．21）pA／pF。从Ⅰ-Ⅴ曲线可见，起搏电流的电流密度具有电压依赖性特征，且病理模型犬的肺静脉肌袖细胞起搏电流电流随超极化电位增加更为明显。在-120mV时，房颤犬静脉肌袖细胞电流的半激活电压为（-84.3±4．9）mV，激活曲线斜率为（＋12．1±2．6）mV，而未处理细胞的半激活电压为（-98.0±7．2）mv，激活曲线斜率为（＋9．5±1．8）mV，明显向更正的电位方向移动，提示老龄房颤犬静脉肌袖起搏电流更易激活。结论：老龄房颤犬静脉肌袖细胞更易出现自动除极电位，起搏电流的密度更高，起搏电流激活也更容易，提示起搏电流可能参与老年房颤异位起搏的发生。

英文摘要：

BACKGROUND： Electropbysiological change is one of the features of aging heart. OBJECTIVE： To construct model of elderly canine with atrial fibrillation so as to observe the characteristics of ectopic automaticity and hyperpolarization activated cation current （If） in pulmonary vein sleeve cardiomyocytes. DESIGN, TIME AND SETTING： Controlled animal trial was performed at the Experimental Animal Center and Institute of Cardiovascular Disease, General Hospital of Chinese PLA between March 2005 and December 2007. MATERIALS： Twelve healthy elderly canine, aged 7-9 years, weighing 15-20 kg, irrespective of gender, were selected. Tyrode＇s solution （mmol/L） contained NaCl 135, KCl 5.4, CaCl2 1.8, MgCl2 1, NaH2PO4 0.33, HEPES 10, glucose 10, and pH was adjusted to 7.4 using NaOH. METHODS： Six canines were subjected to long-term rapidly atrial pacing （8 weeks） to inducing atrial fibrillation model, and the others served as control. Pulmonary vein sleeve cardiomyocytes were isolated from a Landengorff column. If current was measured with the whole-cell patch-clamp technique. MAIN OUTCOME MEASURES： Features of action potential, pacemaker current, Ⅰ-V curve and features of current activation. RESULTS： Spontaneously diastolic depolarization and action potential were recorded in about 82.6% of the model cells, while working myocardial action potential was found in about 40% of the control cells. The rapidly atrial pacing canine PV cardiomyocytes had larger If densities （-2.66±0.4） pA/pF versus （-1.24±0.21） pA/pF in control cells, P 〈 0.01, n=15） at -120 mV. Ⅰ-Ⅴ curve showed that It densities exhibited voltage dependence, and the current in animal model cells significantly changed with increase of hyperpolarization. Furthermore, in the group of rapidly atrial pacing, the half maximal activation potential （V1/2） was （-84.3±4.9） mV and rate of activated curve was （＋ 12.1±2.6） mV, significantly moved to positive potential, while those of control cells were （98.8±7.2