KINETICS AND COMPONENTS OF THE FLASH PHOTOCURRENT OF ISOLATED RETINAL RODS OF THE LARVAL SALAMANDER, AMBYSTOMA-TIGRINUM
KINETICS AND COMPONENTS OF THE FLASH PHOTOCURRENT OF ISOLATED RETINAL RODS OF THE LARVAL SALAMANDER, AMBYSTOMA-TIGRINUM
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DOI：
10.1113/jphysiol.1987.sp016884
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发表时间：
1987-12-01
影响因子：
5.5
通讯作者：
PUGH, EN
中科院分区：
文献类型：
--
作者：
COBBS, WH;PUGH, EN
1.在电流或电压钳模式下，通过组合的细胞外抽吸电极和细胞内紧密密封电极，从分离的蝾螈杆记录由20微秒的强烈闪光（光电流）引发的膜电流。幅度（平均值+/-2 S.E.M.）对于零电流下的电流钳，抽吸和细胞内电极记录的最大光响应分别为40 +/-5 pA（n = 18）和35 +/-7 mV（n = 8）;对于零电流保持电位-24 +/-3 mV下的电压钳，分别为43 +/-9 pA和66 +/-13（n = 11）pA。2.由闪光引发的光电流异构化0.1%或更多的外段的视紫红质实现了饱和速度，并在小于50 ms内完成95%。增加闪光强度以上的0.1%异构化的效果可以被描述为光电流的平移沿着时间轴朝向原点。在0 - 50 ms的时间间隔内，后三分之二的速度饱和光电流被很好地描述为单指数衰减。电压钳模式下的衰减（2.8 +/-1.2 ms，n = 11）比电流钳模式下的衰减（17 +/-5 ms，n = 17）快得多。3.速度饱和光电流的最初三分之一发生在从闪光到指数衰减开始的时间间隔内，在电流和电压钳位中遵循大约相同的时间过程。这个初始的“潜伏”阶段所占用的时间间隔随着闪光强度的增加而减少，并达到约7毫秒的表观最小值，以响应闪光异构化10%或更多的视紫红质在约。22摄氏度。4.通过分析在两种记录模式下连续测量的外段电流之间的差异，支持了外段光敏膜电流衰减在电流钳和电压钳中相同的假设。首先，差电流的尾部呈指数衰减，时间常数约等于R x C，其中R和C是独立估计的杆的斜率电阻和电容。其次，当差电流除以外段电容时，差电流的积分非常接近在电流钳下测量的超偏振光响应。因此，位移电流解释了在电流钳和电压钳中测量的光电流之间的差异。（400字处截断摘要）
1. Membrane currents initiated by intense, 20 microseconds flashes (photocurrents) were recorded from isolated salamander rods by combined extracellular suction electrodes and intracellular tight‐seal electrodes either in current or voltage clamp mode. The magnitudes (mean +/‐ 2 S.E.M.) of the maximal photoresponses recorded by the suction and by the intracellular electrode respectively were 40 +/‐ 5 pA (n = 18) and 35 +/‐ 7 mV (n = 8) for current clamp at zero current; 43 +/‐ 9 pA and 66 +/‐ 13 (n = 11) pA for voltage clamp at the zero‐current holding potential, ‐24 +/‐ 3 mV. 2. Photocurrents initiated by flashes isomerizing 0.1% or more of the outer segment's rhodopsin achieved a saturated velocity and were 95% complete in less than 50 ms. The effect of incrementing flash intensity above 0.1% isomerization can be described as a translation of the photocurrent along the time axis towards the origin. Within the interval 0‐50 ms the latter two‐thirds of the velocity‐saturated photocurrent is well described as a single‐exponential decay. The decay was much faster in voltage clamp (2.8 +/‐ 1.2 ms, n = 11) than in current clamp mode (17 +/‐ 5 ms, n = 17). 3. The initial third of the velocity‐saturated photocurrent, occurring over the interval from the flash to the onset of exponential decay, followed about the same time course in current and voltage clamp. The time interval occupied by this initial 'latent' phase decreased with increasing flash intensity and attained an apparent minimum of about 7 ms in response to flashes isomerizing 10% or more of the rhodopsin at ca. 22 degrees C. 4. The hypothesis that the decay of outer segment light‐sensitive membrane current is the same in current and voltage clamp was supported by an analysis of the difference between outer segment currents measured successively in the two recording modes. First, the tail of the difference current decayed exponentially with a time constant approximately equal to R x C, where R and C are independently estimated slope resistance and capacitance of the rod. Secondly, the integral of the difference current, when divided by outer segment capacitance, closely approximated the hyperpolarizing light response measured under current clamp. Thus, displacement current accounted for the difference between photocurrents measured in current and voltage clamp.(ABSTRACT TRUNCATED AT 400 WORDS)