瑞芬太尼对家兔窦房结起搏细胞自律性的影响

Effects of remifentanil on sinoatrial node autorhythmicity in rabbits

目的评价瑞芬太尼对家兔窦房结起搏细胞自律性的影响。方法健康家兔24只，体重1．8～2．2kg，雌雄不拘，取窦房结组织，采用细胞内玻璃微电极技术记录正常状态下家兔窦房结起搏细胞动作电位为基础值，并进行下述3部分实验（n=8）：（1）采用累积浓度给药法给予瑞芬太尼2、4、8、16、32ng／ml，分别于各浓度药物作用组织15min时记录动作电位；（2）先以16ng／ml的瑞芬太尼作用组织15min，记录动作电位，台氏液洗脱后以含有钙通道开放剂BayK86440．5μmol／L的台氏液灌流标本15min，再以含有瑞芬太尼16ng／ml的灌流液冲灌标本15min，记录动作电位；（3）先以16ng／ml的瑞芬太尼作用组织15min，记录动作电位，台氏液洗脱后以含有钾通道阻滞剂TEA20nmol／L的台氏液灌流标本15min，再以含有瑞芬太尼16ng／ml的灌流液冲灌标本15min，记录动作电位。动作电位参数：动作电位幅值（APA）、窦房结起搏细胞放电的频率（RPF）、复极化90％时间（APD90）和4相自动除极化速度（VDD）。结果与基础值比较，瑞芬太尼使窦房结起搏细胞APA、RPF、VDD降低，APD90延长，且呈浓度依赖性（P〈0．05）。BayK8644预先给药可逆转瑞芬太尼对窦房结起搏细胞的电生理效应，而TEA预先给药后，对瑞芬太尼诱发窦房结起搏细胞的电生理效应无影响。结论瑞芬太尼对家兔窦房结起搏细胞有负性变时作用，该效应与其阻断钙通道有关，与钾通道无关。

Objective To investigate the effects of remifentanil on sinoatrial （SA） node autorhythmicity in rabbits. Methods Twenty-four healthy rabbits of both sexes weighing 1.8-2.2 kg were sacrificed. Their hearts were removed and sinoatrial nodes were dissected and placed in Tyrode solution saturated with 95 % 02-5 % CO2 at 36 ℃ . The action potentials of the sinus node pacemaker cells were recorded by intracellular glass microeleetrode technique. The experiment was performed in 3 parts （ n = 8 each） . Part Ⅰ ： the sinoatrial node was exposed to remifentanil 2, 4, 8, 16 and 32 ng/ml respectively. The action potentials were recorded after the sinoatrial nodes were exposed to each concentration of remifentanil for 15 min. Part Ⅱ and Ⅲ ： the sinoatrial, nodes were first ex- posed to Ca2＋ channel agonist Bay K8644 0.5 μmol/L or K＋ channel blocker TEA 20 nmol/L for 15 rain. Then remifentanil was added until the concentration reached 16 ng/ml （final concentration） and 15 min later the action potentials were recorded. The action potential parameters included, amplitude of action potential （APA）, rate of pacemaker firing （RPF）, action potential duration at 90% repolarization （APD90） and velocity of diastolic depolar- ization （VDD）.Results Remifentanil significantly decreased, APA, RPF, VDD and prolonged APD90 in a con- centration dependent manner as compared with the baseline values. Pretreatment with Bay K8644 could block the effects of remifentanil on SA node pacemaker cells, while TEA did not affect the electrophysiologic effects of remifentanil on SA node pacemaker cells. Conclusion Remifentanil exerts a negative chronotropic action on SAnode pacemaker cells. These effects nels is not involved in these effects.