The membrane current of single rod outer segments
The membrane current of single rod outer segments
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单杆外节膜电流
DOI：
10.1113/jphysiol.1979.sp012715
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发表时间：
1979
期刊：
影响因子：
1.8
通讯作者：
K. Yau
中科院分区：
文献类型：
--
作者：
D. Baylor;T. Lamb;K. Yau
1.将蟾蜍视网膜中单个视杆的外节拉入玻璃吸管中记录膜电流。2.闪光诱发瞬时外向电流。峰值响应幅度与闪光强度相关的米氏方程的半饱和强度约1光子mum-2。3.饱和响应幅度范围高达27 pA，并密切对应于完全抑制的稳定内向电流存在于黑暗中。4.对于一个给定的细胞，饱和响应幅度与吸管外段的长度呈线性关系。这与光敏通道的均匀密度和沿外段沿着可忽略的膜电位梯度一致。5.对明亮闪光的反应从未显示出从先前在细胞内电压记录中看到的初始峰值的弛豫，这表明负责弛豫的电导变化不会发生在外段。6.仅记录的外节对局部照明的反应与使用相同强度的漫射光获得的反应非常相似，这表明外围视杆细胞对反应的贡献很小。7.“红色”视杆的光谱灵敏度与基于视黄醇1的色素一致，λ max = 498 +/-2 nm。8.反应的动力学与影响内部递质作用的延迟的四个阶段一致。反应更快，在基底端的外段比在远端。9.背景光降低了对叠加的暗淡测试闪光的敏感性，并缩短了响应的时程，这表明适应光修改了外段内的转导机制的动力学和增益。10.对昏暗光线的反应表现出明显的波动，这在随后的论文中（Baylor，Lamb & Yau，1979）归因于光的量子性质。
1. Outer segments of individual rods in the retina of the toad, Bufo marinus, were drawn into a glass pipette to record the membrane current. 2. Light flashes evoked transient outward currents. The peak response amplitude was related to flash intensity by a Michaelis equation with half‐saturating intensity about 1 photon mum‐2. 3. The saturating response amplitude ranged up to 27 pA and corresponded closely to complete suppression of the steady inward current present in darkness. 4. For a given cell the saturating response amplitude varied linearly with the length of outer segment within the pipette. This is consistent with a uniform density of light‐sensitive channels and negligible gradient of membrane potential along the outer segment. 5. Responses to bright flashes never showed the relaxation from an initial peak seen previously in intracellular voltage recordings, suggesting that the conductance change responsible for the relaxation does not occur in the outer segment. 6. Responses to local illumination of only the recorded outer segment were very similar to those obtained with diffuse light at the same intensity, indicating that peripheral rods made little contribution to the responses. 7. The spectral sensitivity of 'red' rods was consistent with a retinal1‐based pigment with lambda max = 498 +/‐ 2 nm. 8. The kinetics of the response were consistent with four stages of delay affecting action of the internal transmitter. Responses were faster at the basal end of the outer segment than at the distal tip. 9. Background light reduced the sensitivity to a superposed dim test flash and shortened the time course of the response, indicating that adapting light modifies the kinetics and gain of the transduction mechanism within the outer segment. 10. Responses to dim lights exhibited pronounced fluctuations which are attributed in the succeeding paper (Baylor, Lamb & Yau, 1979) to the quantal nature of light.