Rieke F, Baylor D A
Department of Physiology and Biophysics, University of Washington, Seattle 98195, USA.
Neuron. 2000 Apr;26(1):181-6. doi: 10.1016/s0896-6273(00)81148-4.
Spontaneous fluctuations in the electrical signals of the retina's photoreceptors impose a fundamental limit on visual sensitivity. While noise in the rods has been studied extensively, relatively little is known about the noise of cones. We show that the origin of the dark noise in salamander cones varies with cone type. Most of the noise in long wavelength-sensitive (L) cones arose from spontaneous activation of the photopigment, which is a million-fold less stable than the rod photopigment rhodopsin. Most of the noise in short wavelength-sensitive (S) cones arose in a later stage of the transduction cascade, as the photopigment was relatively stable. Spontaneous pigment activation effectively light adapted L cones in darkness, causing them to have a smaller and briefer dim flash response than S cones.
视网膜光感受器电信号的自发波动对视觉敏感度构成了基本限制。虽然对视杆细胞中的噪声已进行了广泛研究，但对视锥细胞噪声的了解相对较少。我们发现，蝾螈视锥细胞暗噪声的起源因视锥细胞类型而异。长波长敏感（L）视锥细胞中的大部分噪声源于光色素的自发激活，其稳定性比视杆细胞光色素视紫红质低一百万倍。短波长敏感（S）视锥细胞中的大部分噪声出现在转导级联反应的后期，因为光色素相对稳定。自发的色素激活在黑暗中有效地使L视锥细胞适应了光，导致它们比S视锥细胞对昏暗闪光的反应更小且更短暂。
