Department of Human and Information Science, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan.
Department of Living Environmental Science, Fukuoka Women's University, Fukuoka, Fukuoka 813-8529, Japan.
Neuroscience. 2017 Aug 15;357:363-371. doi: 10.1016/j.neuroscience.2017.06.021. Epub 2017 Jun 17.
Since the discovery of intrinsic photosensitive retinal ganglion cell (ipRGC) was reported in 2002, many features specific to this cell type have been described. However, scare information is available on the retinographic components directly reflecting ipRGC activity. In this study, we identified the electroretinogram (microERG) that reflects the photoresponses by ipRGCs in ex vivo preparations of the mouse retina, in which classical photoreceptors (cones and rods) were ablated mechanically and photochemically. MicroERG consisted of three components: a large transient ON response, a small and lazy hump 19s after the onset of the light, and a large transient OFF response. A complete microERG recording required at least 30s of light exposure. MicroERG showed the highest spectral photosensitivity at 478nm. This wavelength corresponds to the peak wavelength in the ipRGCs' photosensitive curve. The psychophysical test using a blue light-emitting diode (LED) light (470nm) revealed that the absolute threshold illuminance for microERG was greater than 12.26 log photons/s/cm in both ON and OFF responses, whereas microERG was not adapted for dark. The amplitude of microERG increased linearly with irradiance. The sensitivity of temporal frequency was high in microERG (at least 100Hz), as suggested by the study on melatonin suppression by flickering light in human subjects (Zelter et al., 2014). Melatonin secretion was suppressed by light via ipRGCs and the suprachiasmatic nucleus. These properties of the photoresponse indicate that microERG may reflect the functions of ipRGC as a luminance detector in the mouse retina.
自 2002 年报道发现内在光敏视网膜神经节细胞(ipRGC)以来，人们已经描述了许多这种细胞类型的特有特征。然而，关于直接反映 ipRGC 活动的视网膜成分的信息很少。在这项研究中，我们在离体培养的小鼠视网膜中鉴定了反映 ipRGC 光反应的视网膜电图（微 ERG），其中经典感光器（视锥细胞和视杆细胞）通过机械和光化学方法被消融。微 ERG 由三个成分组成：一个大的瞬态 ON 反应，一个在光起始后 19 秒的小而缓慢的驼峰，以及一个大的瞬态 OFF 反应。完整的微 ERG 记录至少需要 30 秒的光照。微 ERG 在 478nm 处显示出最高的光谱光敏感性。该波长对应于 ipRGC 光敏感曲线的峰值波长。使用蓝色发光二极管（LED）光（470nm）进行的心理物理测试表明，在 ON 和 OFF 反应中，微 ERG 的绝对阈值照度均大于 12.26 log 光子/s/cm，而微 ERG 对暗适应不敏感。微 ERG 的振幅随辐照度呈线性增加。微 ERG 的时间频率灵敏度较高（至少 100Hz），这正如人类受试者中闪烁光对褪黑素抑制的研究所示（Zelter 等人，2014 年）。褪黑素通过 ipRGC 和视交叉上核的光抑制分泌。这些光反应的特性表明，微 ERG 可能反映了 ipRGC 作为小鼠视网膜中亮度探测器的功能。
