VOLTAGE-DEPENDENCE OF BETA-ADRENERGIC MODULATION OF CONDUCTION IN THE CANINE PURKINJE-FIBER
VOLTAGE-DEPENDENCE OF BETA-ADRENERGIC MODULATION OF CONDUCTION IN THE CANINE PURKINJE-FIBER
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DOI：
10.1161/01.res.75.3.511
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发表时间：
1994-09-01
影响因子：
20.1
通讯作者：
PACKER，DL
中科院分区：
文献类型：
--
作者：
MUNGER，TM;JOHNSON，SB;PACKER，DL
尽管最近的电压钳和微电极研究已经证明 Na+ 电流 (INa) 的 β 肾上腺素能调节，但儿茶酚胺对传导的调节以及该过程的电压依赖性尚未阐明。为了确定在β-肾上腺素能激动剂存在的情况下是否发生电压依赖性传导调节，通过使用双微电极技术检查了1μmol/L异丙肾上腺素对犬浦肯野纤维中脉冲传播的影响。在生理膜电位 ([K+]o 5.4 mmol/L) 下，异丙肾上腺素将平方传导速度 [theta 2, 0.39 +/- 0.25 (m/s)2 (平均值 +/- SD)] 从 3.46 +/- 0.86 增加到 3.85 +/- 0.98 (m/s)2 (P < .011)，变化为 11%，但不改变动作电位第 0 相上坡的最大一阶导数（Vmax，641 +/- 50 与 657 +/- 47 V/s，P = NS）。在通过 12 mmol/L [K+]o 滴定产生的 -65 mV 跨膜电位下，θ 2 下降 79% 至 0.73 +/- 0.44 (m/s)2，同时 Vmax 下降 85% 至 95 +/- 43 V/s (P < .02)。添加异丙肾上腺素进一步将 θ 2 降低至 0.49 +/- 0.33 (m/s)2 (P = .02)，同时 Vmax 进一步降低至 51 +/- 25 V/s (P < .05)。异丙肾上腺素使由 theta 2 和 Vmax 生成的表观 Na+ 通道可用性曲线产生 3 mV 超极化偏移，用作快速向内 INa 的指标，而不改变关系的斜率。在一定范围的去极化电位范围内，归一化 theta 2 和 Vmax 之间的关系是线性的，并且异丙肾上腺素不会明显改变。（摘要截断为 250 字）
Although recent voltage-clamp and microelectrode studies have demonstrated beta-adrenergic modulation of Na+ current (INa) the modulation of conduction by catecholamines and the voltage dependence of that process have not been elucidated. To determine whether voltage-dependent modulation of conduction occurs in the presence of a beta-adrenergic agonist, the effect of 1 mumol/L isoproterenol on impulse propagation in canine Purkinje fibers was examined by using a dual-microelectrode technique. At physiological membrane potentials ([K+]o 5.4 mmol/L), isoproterenol increased squared conduction velocity [theta 2, 0.39 +/- 0.25 (m/s)2 (mean +/- SD)] from 3.46 +/- 0.86 to 3.85 +/- 0.98 (m/s)2 (P < .011), an 11% change, without altering the maximum first derivative of the upslope of phase 0 of the action potential (Vmax, 641 +/- 50 versus 657 +/- 47 V/s, P = NS). At transmembrane potential of -65 mV, produced by 12 mmol/L [K+]o titration, theta 2 declined 79% to 0.73 +/- 0.44 (m/s)2 as Vmax decreased 85% to 95 +/- 43 V/s (P < .02). The addition of isoproterenol further decreased theta 2 to 0.49 +/- 0.33 (m/s)2 (P = .02) in parallel with a further decline in Vmax to 51 +/- 25 V/s (P < .05). Isoproterenol produced a 3-mV hyperpolarizing shift of apparent Na+ channel availability curves generated from both theta 2 and Vmax, used as indexes of the fast inward INa, without changing the slopes of the relation. The relation between normalized theta 2 and Vmax over a range of depolarized potentials was linear and was not appreciably altered by isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)