Zhou X, Ideker R E, Blitchington T F, Smith W M, Knisley S B
Department of Medicine, Duke University Medical Center, Durham, NC, USA.
Circ Res. 1995 Sep;77(3):593-602. doi: 10.1161/01.res.77.3.593.
To study the optical transmembrane potential change (delta F) induced during shocks, optical recordings were obtained in 15 isolated perfused rabbit hearts treated with the potentiometric dye di-4-ANEPPS and diacetyl monoxime. Shock electrodes were sutured on the right and left ventricles. A laser beam 30 microns in diameter was used to optically excite di-4-ANEPPS. Fluorescence from a region 150 microns in diameter was recorded during a shock. In the macroscopic study (six animals), there were nine recording spots that were 3 mm apart between the two shock electrodes. In the microscopic study, there were three recording regions that were 3 mm away from either shock electrode and midway between them, with nine recording spots that were 30 microns (three animals), 100 microns (three animals), and 300 microns (three animals) apart in each region. After 20 S1 stimuli, a 10-ms truncated exponential S2 shock of defibrillation-threshold strength was given during the plateau of the last S1 action potential. In the microscopic study, shocks were also given during diastole, with delta F recordings at the three recording regions. Shocks of both polarities were tested. delta F during the shock was expressed as a percentage of the fluorescence change during the S1 upstroke action potential amplitude (the S1 Fapa), ie, delta F/Fapa%. In the macroscopic study, the magnitudes of delta F/Fapa% from recording spots 1 to 9, numbered from the left to the right ventricular electrodes, were 77 +/- 41%, 46 +/- 32%, 32 +/- 27%, 28 +/- 20%, 37 +/- 25%, 24 +/- 20%, 33 +/- 22%, 37 +/- 25%, and 59 +/- 29%, respectively (P < .05 among the nine spots). Depolarization or hyperpolarization could occur near either shock electrode with both shock polarities, but the magnitude of hyperpolarization was 1.8 +/- 0.9 times that of depolarization at the same recording spot when the shock polarity was reversed (P < .01). In the microscopic study, the change in delta F/Fapa% varied significantly over the microscopic regions examined. The maximum values of delta F/Fapa% for hyperpolarizing shocks during diastole reached only 7 +/- 10% of those for shocks during the plateau (P < .01). During diastole, the time until a new action potential occurred after the beginning of the shock was shorter when the membrane was depolarized (1.1 +/- 0.5 ms) than when it was hyperpolarized (12.8 +/- 9.1 ms, P < .01). Conclusions are as follows: (1) A shock can induce either hyperpolarization or depolarization. (2) Hyperpolarization or depolarization during a shock can occur near either the anodal or cathodal shock electrode. (3) Variation of delta F/Fapa% exists within a microscopic region.(ABSTRACT TRUNCATED AT 400 WORDS)
为研究电击期间诱导产生的光学跨膜电位变化（δF），对15只经电位染料di - 4 - ANEPPS和双乙酰单肟处理的离体灌注兔心脏进行了光学记录。电击电极缝在左右心室上。使用直径30微米的激光束对di - 4 - ANEPPS进行光学激发。在电击期间记录直径150微米区域的荧光。在宏观研究（6只动物）中，两个电击电极之间有9个记录点，彼此相距3毫米。在微观研究中，有3个记录区域，分别距离任一电击电极3毫米且位于它们中间，每个区域内有9个记录点，彼此相距30微米（3只动物）、100微米（3只动物）和300微米（3只动物）。在20次S1刺激后，在最后一次S1动作电位的平台期给予一次10毫秒截断指数形式的除颤阈值强度的S2电击。在微观研究中，也在舒张期给予电击，并在3个记录区域记录δF。对两种极性的电击都进行了测试。电击期间的δF表示为S1上升动作电位幅度期间（S1 Fapa）荧光变化的百分比，即δF/Fapa%。在宏观研究中，从左心室电极到右心室电极编号的记录点1至9的δF/Fapa%大小分别为77±41%、46±32%、32±27%、28±20%、37±25%、24±20%、33±22%、37±25%和59±29%（9个点之间P <.05）。两种电击极性时，在任一电击电极附近均可发生去极化或超极化，但当电击极性反转时，同一记录点处超极化的幅度是去极化幅度的1.8±0.9倍（P <.01）。在微观研究中，在所检查的微观区域内，δF/Fapa%的变化显著。舒张期超极化电击时δF/Fapa%的最大值仅为平台期电击时的7±10%（P <.01）。在舒张期，电击开始后到新动作电位出现的时间，膜去极化时（1.1±0.5毫秒）比超极化时（12.8±9.1毫秒，P <.01）短。结论如下：（1）电击可诱导超极化或去极化。（2）电击期间的超极化或去极化可发生在阳极或阴极电击电极附近。（3）微观区域内存在δF/Fapa%的变化。（摘要截断于400字）
