Frishman L J, Sieving P A, Steinberg R H
Department of Physiology, University of California, San Francisco 94143-0444.
Vis Neurosci. 1988;1(3):307-15. doi: 10.1017/s0952523800001966.
We have investigated responses in proximal retina of the cat that contribute to two kinds of electroretinogram (ERG) recordings: (1) the pattern ERG, a light-adapted response and (2) the threshold and near threshold ERG, a dark-adapted response (Sieving et al., 1986a, 1986b; Sieving & Steinberg, 1985). In intraretinal, extracellular recordings, two negative-going responses were identified that are maximal around the inner plexiform layer, and distinct from PII, which is maximal in distal retina: under light-adapted conditions, a spatially tuned response at light and light offset, the "M-wave" (previously described in cold-blooded animals by Karwoski & Proenza (1977, 1980)), and under dark-adapted conditions, the scotopic threshold response, or "STR," a response at light onset. The results under dark-adapted conditions are examined in more detail here. The STR is a very sensitive response whose threshold is 1.5-2.0 log units below that of the dc-component of PII and therefore well below the threshold of the a-, b-, and c-waves. It saturates about 2.4 log units below rod saturation. The STR contributes a negative-going potential to the dark-adapted ERG that is dominant near threshold; while PII (dc-component and b-wave) contributes a positive-going potential that is dominant at higher intensities (Sieving et al., 1986b). Investigation of the mechanism of the proximal retinal responses that contribute to the ERG supports of K(+)-Müller cell hypothesis of their origin.
我们研究了猫近端视网膜的反应，这些反应有助于两种视网膜电图（ERG）记录：（1）图形ERG，一种明适应反应；（2）阈值和近阈值ERG，一种暗适应反应（Sieving等人，1986a，1986b；Sieving和Steinberg，1985）。在视网膜内细胞外记录中，识别出两种负向反应，它们在内网状层附近最大，与在远端视网膜中最大的PII不同：在明适应条件下，对光和光熄灭的空间调谐反应，即“M波”（先前由Karwoski和Proenza（1977，1980）在冷血动物中描述），以及在暗适应条件下，暗视阈值反应，或“STR”，对光开始的反应。这里更详细地研究暗适应条件下的结果。STR是一种非常敏感的反应，其阈值比PII的直流成分低1.5 - 2.0对数单位，因此远低于a波、b波和c波的阈值。它在视杆饱和以下约2.4对数单位时饱和。STR对暗适应ERG贡献一个负向电位，在阈值附近占主导；而PII（直流成分和b波）贡献一个正向电位，在较高强度时占主导（Sieving等人，1986b）。对有助于ERG的近端视网膜反应机制的研究支持了其起源的K⁺ - 米勒细胞假说。
