Bonezzi Paul J, Stabio Maureen E, Renna Jordan M
a Department of Biology , The University of Akron , Akron , Ohio , USA.
b Department of Cell and Developmental Biology , University of Colorado School of Medicine , Aurora , CO , USA.
Curr Eye Res. 2018 May;43(5):666-673. doi: 10.1080/02713683.2018.1433859. Epub 2018 Feb 15.
Photoreceptors in the mouse retina express much of the molecular machinery necessary for phototransduction and glutamatergic transmission prior to eye opening at postnatal day 13 (P13). Light responses have been observed collectively from rod and cone photoreceptors via electroretinogram recordings as early as P13 in mouse, and the responses are known to become more robust with maturation, reaching a mature state by P30. Photocurrents from single rod outer segments have been recorded at P12, but no earlier, and similar studies on cone photoreceptors have been done, but only in the adult mouse retina. In this study, we wanted to document the earliest time point in which outer retinal photoreceptors in the mouse retina begin to respond to mid-wavelength light.
Ex-vivo electroretinogram recordings were made from isolated mouse retinae at P7, P8, P9, P10, and P30 at seven different flash energies (561 nm). The a-wave was pharmacologically isolated and measured at each developmental time point across all flash energies.
Outer-retinal photoreceptors generated a detectable response to mid-wavelength light as early as P8, but only at photopic flash energies. a-wave intensity response curves and kinetic response properties are similar to the mature retina as early as P10.
These data represent the earliest recorded outer retinal light responses in the rodent. Photoreceptors are electrically functional and photoresponsive prior to eye opening, and much earlier than previously thought. Prior to eye opening, critical developmental processes occur that have been thought to be independent of outer retinal photic modulation. However, these data suggest light acting through outer-retinal photoreceptors has the potential to shape these critical developmental processes.
小鼠视网膜中的光感受器在出生后第13天（P13）睁眼之前就表达了光转导和谷氨酸能传递所需的大部分分子机制。早在小鼠出生后第13天，通过视网膜电图记录就已观察到视杆和视锥光感受器的集体光反应，并且已知这些反应会随着成熟而变得更强，到P30时达到成熟状态。早在P12时就已记录到单个视杆外段的光电流，但更早时尚未记录到，并且对视锥光感受器也进行了类似研究，但仅在成年小鼠视网膜中进行。在本研究中，我们想要记录小鼠视网膜外层光感受器开始对中波长光作出反应的最早时间点。
在P7、P8、P9、P10和P30时，从分离的小鼠视网膜上以七种不同的闪光能量（561 nm）进行离体视网膜电图记录。在所有闪光能量下的每个发育时间点，通过药理学方法分离并测量a波。
早在P8时，视网膜外层光感受器就对中波长光产生了可检测到的反应，但仅在明视闪光能量下。早在P10时，a波强度反应曲线和动力学反应特性就与成熟视网膜相似。
这些数据代表了啮齿动物中最早记录到的视网膜外层光反应。光感受器在睁眼之前就具有电功能且对光有反应，并且比之前认为的要早得多。在睁眼之前，会发生一些关键的发育过程，这些过程被认为与视网膜外层光调制无关。然而，这些数据表明，通过视网膜外层光感受器起作用的光有可能塑造这些关键的发育过程。
