Sieving P A, Frishman L J, Steinberg R H
J Neurophysiol. 1986 Oct;56(4):1039-48. doi: 10.1152/jn.1986.56.4.1039.
There has been relatively little known about responses from proximal retina in mammals that could contribute to the electroretinogram (ERG). Recently, there has been evidence that the proximal retina is involved in generating the pattern electroretinogram (PERG). In the present work we investigated proximal retinal activity in the intact cat eye during light adaptation. Extracellular potentials evoked in response to circular spots of light, flashed on steady backgrounds, were recorded with microelectrodes placed intraretinally at different depths. Prominent negative responses were found in proximal retina that could be identified as the M-wave previously observed only in cold-blooded retinas. Like the cold-blooded responses, the cat's M-wave consisted of negative-going potentials at stimulus onset and offset that were maximum in amplitude with small spots. By analogy to the cold-blooded data, the cat M-wave is presumed to be the extracellular voltage arising from Müller cell responses to K+ released by proximal retinal neurons. In addition, the cat M-wave only appeared with backgrounds at and above rod saturation and had short latencies (30 ms) at stimulus onset and offset, indicating that it is a cone-driven response. The M-wave could be clearly distinguished from PII (b-wave and DC component) on the basis of its form, depth distribution, and stimulus-response characteristics. For example, photopic PII had its maximum voltage in the distal retinal at 55% retinal depth, whereas the M-wave was maximal in the proximal retina at 25% retinal depth. Also, PII simply increased in amplitude as stimulus spots were enlarged, whereas the M-wave exhibited spatial tuning. Under light-adapted conditions and with small-spot stimuli the M-wave is the largest extracellular voltage in cat retina. By recording the vitreal ERG near the retinal surface with the microelectrode referenced to a silver wire in the vitreous, we found that the M-wave in response to a small spot always had a negative polarity in the vitreous. Thus, unlike PII, the M-wave does not reverse polarity at the vitreo-retinal border. Because of stray-light effects, however, we were not able to assess the amplitude of the M-wave's contribution to the ERG obtained with diffuse retinal illumination. We conclude that the M-wave is present in the cat as a prominent cone-driven response of proximal retina that is separate from the b-wave, and whose significance for electroretinographic recordings remains to be determined.
关于哺乳动物近端视网膜对视网膜电图（ERG）可能产生的反应，人们了解相对较少。最近，有证据表明近端视网膜参与了图形视网膜电图（PERG）的产生。在本研究中，我们调查了完整猫眼在明适应过程中近端视网膜的活动。用微电极置于视网膜内不同深度，记录在稳定背景上闪烁的圆形光斑诱发的细胞外电位。在近端视网膜中发现了明显的负反应，这可以被识别为先前仅在冷血动物视网膜中观察到的M波。与冷血动物的反应一样，猫的M波由刺激开始和结束时的负向电位组成，小光斑时幅度最大。类比冷血动物的数据，推测猫的M波是由Müller细胞对近端视网膜神经元释放的K+做出反应而产生的细胞外电压。此外，猫的M波仅在杆细胞饱和及以上的背景下出现，刺激开始和结束时潜伏期较短（30毫秒），表明它是一种由视锥细胞驱动的反应。基于其波形、深度分布和刺激 - 反应特性，M波可以与PII（b波和直流成分）明显区分开来。例如，明视PII在视网膜远端55%视网膜深度处电压最大，而M波在近端视网膜25%视网膜深度处最大。此外，随着刺激光斑增大，PII的幅度只是简单增加，而M波表现出空间调谐。在明适应条件下和小光斑刺激时，M波是猫视网膜中最大的细胞外电压。通过将微电极参考玻璃体内的银线，在视网膜表面附近记录玻璃体内的ERG，我们发现对小光斑的反应中，M波在玻璃体内总是具有负极性。因此，与PII不同，M波在玻璃体 - 视网膜边界处不会反转极性。然而，由于杂散光效应，我们无法评估M波对漫射视网膜照明下获得的ERG的贡献幅度。我们得出结论，M波在猫中作为近端视网膜的一种明显的视锥细胞驱动反应存在，它与b波不同，其在视网膜电图记录中的意义仍有待确定。
