THE PROPERTIES OF SINGLE CONES ISOLATED FROM THE TIGER SALAMANDER RETINA
THE PROPERTIES OF SINGLE CONES ISOLATED FROM THE TIGER SALAMANDER RETINA
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DOI：
10.1113/jphysiol.1982.sp014263
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发表时间：
1982-01-01
影响因子：
5.5
通讯作者：
WILSON, M
中科院分区：
文献类型：
--
作者：
ATTWELL, D;WERBLIN, FS;WILSON, M
采用电压钳技术，在视觉控制下插入2个微电极，研究了单个视锥细胞的特性。当用2个电极刺穿时，单个锥体具有高达270 M Ω的输入电阻。这可能低于真实的膜电阻，因为穿刺电极的损坏。视锥细胞电容为apprx。85 pF [皮法拉第]。视锥膜包含由电压控制的时间依赖性电流IB和单独的光敏电流。门控电流IB是具有反转电位aptx的内向电流。-25毫伏。在-30至-80 mV范围内通过超极化激活，在恒定电压下遵循一级（指数）动力学。门控时间常数在静息电位为-45 mV时通常为50 ms，在-70 mV时升高至170 ms，并在进一步超极化时降低。锥体光反射的光谱灵敏度曲线在620 nm波长处达到峰值，并且比基于维生素A2的色素的诺模图窄。孤立视锥细胞的光响应是光谱单变的。电压钳位光电流记录在不同的膜电位为各种强度的光阶跃。光电流在apprx处反转。-8 mV。对于给定的强度，光电流的时间过程近似与电压无关（尽管其madness是电压依赖性的）。光敏电流的峰值电流-电压关系的形状与光强无关（尽管其大小与光强有关）。这些结果可以解释，如果光只是简单地改变光敏通道开放的数量，而不改变开放通道的性质，如果控制内部递质产生的反应，内部递质与光敏通道的结合以及通道的关闭和打开不受锥膜中电场的影响，即使这些反应中的至少一些发生在膜中。IB在对光的锥体电压响应的成形中仅起很小的作用。
The properties of isolated single cones were studied using the voltage-clamp technique, with 2 micro-electrodes inserted under visual control. Single cones had input resistances, when impaled with 2 electrodes, of up to 270 M.OMEGA.. This is probably lower than the true membrane resistance, because of damage by the impaling electrodes. The cone capacitance was .apprx. 85 pF [picoFaraday]. The cone membrane contains a time-dependent current, IB, controlled by voltage, and a separate photosensitive current. The gated current, IB, is an inward current with a reversal potential .apprx. -25 mV. It is activated by hyperpolarization over the range -30 to -80 mV, and at constant voltage obeys 1st order (exponential) kinetics. The gating time constant is typically 50 ms at the resting potential of -45 mV, rises to 170 ms at -70 mV and decreases for further hyperpolarization. The spectral sensitivity curve of the cone light repsonse peaks at 620 nm wave-length and is narrower than the nomogram for vitamin A2-based pigments. The light responses of isolated cones are spectrally univariant. Voltage-clamped photocurrents were recorded at various membrane potentials for light steps of various intensities. The photocurrent reversed at .apprx. -8 mV. The time course of the photocurrent, for a given intensity, was approximately independent of voltage (although its madnitude was voltage-dependent). The shape of the peak current-voltage relation of the light-sensitive current was independent of light intensity (although its magnitude was intensity-dependent). These results can be explained if light simply changes the number of photosensitive channels open, without altering the properties to an open channel, and if the reactions controlling the production of internal transmitter, the binding of internal transmitter to the photosensitive channels and the closing and opening of the channels are unaffected by the electric field in the cone membrane, even though at least some of these reactions take place in the membrane. IB plays only a small role in shaping the cone voltage response to light.