CONFUCTION OF CARDIAC IMPULSE .2. SUMMATION AND INHIBITION
CONFUCTION OF CARDIAC IMPULSE .2. SUMMATION AND INHIBITION
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DOI：
10.1161/01.res.28.2.220
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发表时间：
1971-01-01
影响因子：
20.1
通讯作者：
HOFFMAN, BF
中科院分区：
文献类型：
--
作者：
CRANEFIELD, PF;HOFFMAN, BF
切除的犬浦肯野纤维束会产生抑制的兴奋性和反应性。将 8 毫米长的节段包裹在含有 47 mMK+ 的琼脂中，使节段凹陷，琼脂外的束末端保持正常。任一正常端均可通过细胞外电极被激发。通过每端和凹陷段内的细胞内微电极记录动作电位。凹陷段内的传导速度降至 0.05 m/sec。通过凹陷节段的脉冲传输异常包括延迟、2:1 阻滞、较高程度的阻滞、速率依赖性阻滞和显示文克巴赫现象的阻滞。所见传导不对称包括单向阻滞。凹陷节段动作电位波幅低，上行缓慢。当传导失败或非常缓慢以及冲动下降时，动作电位持续时间的变化发生在凹陷节段。传导延迟过大而不能简单地由缓慢的上行引起，归因于细胞合胞体中跨块区域的兴奋事件的总和。结果证明，在受到高 K+ 作用的浦肯野纤维短段中可能会发生足够大的传导延迟，以允许重新进入。
Depressed excitability and responsiveness were created in excised bundles of canine Purkinje fibers. A segment 8 mm long was depressed by being encased in agar containing 47 mMK+, the ends of the bundle outside the agar remaining normal. Either normal end could be excited through extracellular electrodes. Action potentials were recorded by intracellular microelectrodes at each end and within the depressed segment. Conduction velocity within the depressed segment fell as low as 0.05 m/sec. Abnormalities of impulse transmission through the depressed segment included delay, 2:1 block, higher degrees of block, rate-dependent block, and block showing the Wenckebach phenomenon. Asymmetries of conduction seen included one-way block. Action potentials in the depressed segment were of low amplitude and showed slow upstrokes. Variations in action potential duration occurred in the depressed segment when conduction failed or was very slow and when impulses were dropped. Delay in conduction too great to result simply from a slow upstroke is attributed to summation of excitatory events across regions of block in a syncytium of cells. The results prove that conduction delays great enough to permit re-entry can occur in short segments of Purkinje fibers subjected to high K+.